A sliding scale of citrus curds.
To melt or mount.
Hello, welcome to newsletter no. 7. Thank you for taking the time to be here; in only a few weeks, this has become a place I look forward to being each week. Aside from being a cathartic process to empty one’s head of thoughts, ideas and musings, it also puts a metaphorical boot up one’s behind and forces me to organise the many recipes I have been developing and gathering over the last ten years.
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The what, how and why of fruit curds…
A curd is an essential back pocket recipe to have about your person, especially during citrus season. It is versatile in three major areas -
Formulation
Preparation
Application
Fruit curd is commonly made with citrus juice, but as a general rule, it can be made with the juice/puree of other fruits as long as it is paired with some citrus juice too. For this newsletter, we’ll be sticking to the citrus kind.
Formulation
At its most basic, a curd is made with citrus juice and zest, eggs (whole, yolk alone or a combination of the two) and sugar, with some recipes calling for the addition of butter.
Essentially -
Curd = acid + binder/thickener + sweetener + fat (optional)
Already here, you can see how the formula for a curd can slide from the more opulent end (high in yolk and butter) to the more frugal (whole eggs with minimal or zero butter).
Preparation
The methods you’re likely to come across fall into two camps: Camp Melt or Camp Mount. Each method is likely to prescribe varying ratios of the essential ingredients, i.e. the formulation and as such, the different methods and formulas will produce different results.
Method 1 - Camp Melt -
The juice, zest, eggs and sugar are whisked together and then gently heated over a bain marie until sufficiently thick. If butter is part of the formula, it may be added along with the other ingredients at the start or added once the curd has thickened.
In both scenarios, the butter melts completely into the curd.
Method 2 - Camp Mount -
I like to think of this as curd in reverse, a method I first came across via Dorie Greenspan (who came by the recipe from Pierre Hermé), and I noted it again in the iconic Lemon Tart recipe by Liz Prueitt of Tartine.
Rather than adding the butter at the beginning or melting it into hot curd at the end, butter is mounted into the curd once it has started to cool. For this method to work, the butter must be in a cool but pliable state and emulsified into the curd with vigorous whisking or the power of a food processor. It’s a method that resembles the technique known as ‘monter au beurre’, literally to mount with butter, which is used in classic French sauces.
As the butter is emulsified into the curd at a cooler temperature, it does not melt, i.e. the milk solids and butter fat do not separate.
This produces a distinctly different mouthfeel to a curd made via the melt method and results in a curd that carries flavour in a different way. Fat is an unrivalled carrier of flavour; the emulsified fat holds the punch of the citrus right to the end, feels luscious and creamy and releases more nuanced notes as it melts in the mouth. I often think it’s a much softer, more refined, but no less intense recital of citrus.
Understanding ingredients and techniques instead of following a recipe will make for more intuitive and creative baking. Once you know the parameters, the rest is up for improvisation and imaginative play.
This does not mean needing to know everything about a particular recipe, formula or technique but knowing enough so that you can play around and shift the parameters to suit the situation. Just enough to know if substituting an ingredient, tweaking a ratio or streamlining a method will work for you.
Application
I try to refrain from suggesting one recipe for anything over another is ‘better’ or ‘the best’ as it all comes down to context, what you have available to you and what you’re hoping to achieve with it.
If, for example, you have a glut of zested citrus (I’m talking bakery-sized glut) but no use for the juice, then you could make quite a lot of curd (minus the zest). To make a rich curd using the Mount method would be to squander a lot of expensive eggs and butter with no real chance of using up a large batch of perishable curd. In this instance, I’d probably adopt the more streamlined melt method. Using whole eggs and a small amount of butter would turn out a curd with an upfront punch with good acidity and brightness and would take better to freezing. It would come into its own when added to something that can round off its harsh corners, a useful component within something, such as a bread and butter pudding, a topping for Bostock, a ripple in an ice cream sundae, or to balance the sweetness of pavlovas when combined with whipped cream.
If you have some particularly lush citrus, intact and in perfect condition, that you want to showcase, then the Mount method is the way to go. The higher ratio of butter in the formula and the preparation technique renders something more akin to whipped Crème mousseline and can be used in a similar way. My favourite ways to use this style of curd include piping directly into choux buns or sweet shortcrust pastry cases. In addition, it can be used to fill multilayered Gerbeaud-style cakes or roll up a roulade and as a component in plated desserts. Its versatility knows no bounds and is my preferred way to make curd if the situation allows.
This brings us to this week's recipe, Lime Butter Curd, to demonstrate the Mount method because if I had to admit to a ‘best’, then in my heart of hearts, this is ‘the best’ way to make citrus fruit curd.
Those who subscribe to the Extra Credit portion of the newsletter will find a downloadable pdf with all the details to make these Lime Butter Curd Tarts, including a recipe for a sweet shortcrust pastry made with flavourful black wheat flour.
Lime Butter Curd
Limes are not the most fun to juice, but the last few Mexican Limes from the Todolí Citrus haul seemed just the right candidates for this small batch of curd.
As I mentioned, you can improvise within the set parameters; I use whole eggs rather than egg yolks as I feel the amount of butter in this version brings enough richness. The acidity of your citrus will dictate whether or not you want to increase or decrease the sugar and butter to round out the flavour to your liking. I find 100g sugar and 130g butter for every 90-100ml citrus juice a happy place for limes and lemons. When it comes to sweet orange varieties, I’d taste the juice and be prepared to dial down the sugar a little or make up the amount of juice required with a tablespoon or two of lemon juice to bring the necessary acidity.
Ingredients
Yields approx 350g
100g caster sugar
Zest of 2 limes
2 whole eggs
90ml lemon juice
130g unsalted butter (cool room temp, not soft, cubed to 1-2cm)
1/8 tsp sea salt to season
Method
Place the sugar and the lime zest in a heatproof bowl and stir together; the sugar will bruise the zest and release more aromatic oils.
Whisk the whole eggs into the sugar, followed by the lime juice.
Place the bowl over a pan of gently simmering water, and ensure the water does not touch the base of the bowl.
Whisk the mixture until it begins to warm and thicken; use a thermometer to get the temperature to 82 degrees C; whisk intermittently until it reaches this temperature to ensure the eggs do not scramble.
Once the mixture reaches 82 degrees C, remove it from the heat and cool it to 60 degrees C. If the mixture has any lumps, pass through a fine mesh sieve to remove them before cooling.
Place the mixture in the food processor. With the motor running, add five cubes of butter at a time, only adding more when fully incorporated.
Once all the butter has been added, add the sea salt and blend for 3 minutes to ensure the curd is well emulsified.
You can use the curd immediately or store it in a piping bag or an airtight box in the fridge until needed; it should last up to 5 days. For more extended storage, pour the curd into sterilised jars and seal them. It will keep in the refrigerator unopened for up to two weeks.
Once opened, expect it to last between 3-5 days.