I’ll be frank with you, this pie is something of a commitment. It needs starting the night before, with two separate trips to the oven and two to the fridge, but the result is fantastically worth it.
I make this in a 15cm (six inch) deep cake tin; although it looks smaller when presented to guests or family, the depth on it is astounding, and the ratio of lime cream to base works very well. As a naturally clumsy person, I find that smaller, deeper crumb crust pies are easier to handle, with less chance of cracking than their wider, slender counterparts. If you use a thinner tin, reduce the cooking time accordingly.
I used standard limes for this, as key limes are hard to come by in May in Southend on Sea, and when I was researching this recipe, the general consensus seemed to be that although key limes are traditional, other limes are acceptable. Some cooks use a blend of limes and lemons to achieve the tart, slightly unripe sourness of a true key lime, so you could do that, I suppose. I’d suggest one lemon to three limes, if you wanted to try it.
Serves 6 from 66p each. (This post is not sponsored; I provide links to the ingredients that I use so you can see how I calculate my recipe costs, and I may earn a small commission if you click the links or purchase any ingredients.)
250g Biscoff biscuits, or ginger nuts, £1
75g butter/baking spread, 18p
3 medium eggs, 42p
4 limes, 85p
400g can (approx) of condensed milk, 75p
150ml double cream, 70p
30g/4 tbsp icing sugar, 5p
First, place your cake tin on your greaseproof paper, and draw around it carefully to make the lining for the base. It’s important that this covers the base of the tin only, as any intrusion up the sides will compromise the structural integrity of the pressed crumb walls. Cut it out neatly, and place it into the centre of the cake tin. Lightly grease the whole tin, including the paper, and set to one side for now. Preheat your oven to 160C, and place a shelf just below the middle.
Smash your biscuits into crumbs – there are a few ways to do this, depending on what you have at your disposal. If you are lucky enough to have a food processor or magimix, pulse them to a fine crumb. The same effect can be achieved in a bullet blender, in batches, pulsing for 30 seconds at a time so as not to overwork the motor. If you don’t have either of these, you can go old school; pop them in a freezer bag and run them over repeatedly with a rolling pin or round glass bottle, like a wine bottle. However you achieve them, tip your crumbs into a large mixing bowl. Melt your butter, either very quickly on a low heat in a saucepan on the hob, or in the microwave for 30 seconds, and mix well into the crumbs until well combined and evenly coated.
Spoon the buttery crumbs into the greased cake tin, and carefully press them into the base and up the sides. The sides are a little frustrating to do, but persevere with them as they form the structure of the pie. They need only be around 3mm thick at the top, but the seam, where they meet the base, should be thick and rounded. Press the crumbs in firmly with your fingertips, but not so hard that it cracks. Continue until all the crumbs are used up and the base is roughly even, and fairly firm.
Place the cake tin on the centre shelf of the oven, and bake for 12 minutes exactly. Remove, and set to one side for at least 30 minutes to cool.
When the base has cooled, make the lime cream filling. First zest the limes, if using fresh ones, using either a microplane, mini grater, or the small holes on a box grater. You want to grate all the zest off, until not a speck of green remains, but avoid getting too much of the white pith into the mix, as it can be a little bitter. Set the zest to one side. Halve the limes and set aside.
Separate the eggs into two bowls, a large mixing bowl for the yolks and a small bowl or clean jar for the whites. Pop the whites in the fridge to use for something else – I like to make meringues with mine as an accompaniment to any dessert that uses yolks only, but you can also use them in a light victoria sponge, for pancakes, an egg white omelette, or egg fried rice, for example. Whisk the yolks for a few minutes until pale and fluffy. Add the condensed milk and beat vigorously for around five minutes, then add the juice from each lime half, one at a time, beating thoroughly between each one. Fold in most of the lime zest. Pour the lime cream into the cake tin, filling three quarters of the way full. Place back into the oven and bake for 22 minutes, until gently firm to touch. Remove and cool, then transfer to the fridge to chill – for at least two hours, but ideally overnight.
30 minutes before serving: whip the cream and icing sugar together until very stiff. Spread evenly on the top of the pie, smoothing the top with a palette knife or the flat side of a heavy chefs knife. Sprinkle with remaining crumbs and lime zest, and return to the fridge to chill.
To serve, carefully, very carefully, push the pie out from the bottom of the tin. Cautiously insert the tip of a large, heavy knife between the base of the tin and the greaseproof paper to loosen it, and transfer to a flat plate or board. Slice into six even pieces, and serve.
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All text copyright Jack Monroe.
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