Crust
- Line a small mold (16 cm in diameter) with parchment paper.
- Melt the butter.
- In a food processor, grind the biscuits to a fine powder (you can also do this by hand, crushing them or sealing them in a freezer bag and rolling over them with a rolling pin).
- Add the sugar, salt, and cinnamon (if using) to the biscuit crumbs and mix.
- Add the melted butter and stir with a spatula until everything comes together.
- Spread the mixture across the bottom of the mold and press firmly to form a compact, even layer.
- Set in the freezer or refrigerator for 15 to 30 minutes.
- Meanwhile, preheat the oven to 180°C.
- Bake for 12 minutes (adjust for your oven; the crust should have darkened slightly).
Lime Cream
- Zest 2 limes (the zest should be very fine).
- Add the zest to the egg yolks and whisk on high speed for 5 to 10 minutes, until pale and frothy.
- Add the condensed milk and whisk on high speed for 3 to 5 minutes, until light and airy.
- Add the lime juice and gently fold in with a spatula until smooth.
Baking and Resting
- Pour the cream over the baked crust.
- Lower the oven to 160°C and bake for 20 minutes (start checking at 17 minutes).
- To check doneness: gently shake the mold. The edges should be mostly set, but the center should still wobble.
- Let cool at room temperature for 30 minutes, then refrigerate for at least 2 hours.
- Take out of the fridge 15 minutes before serving.