Before you start, line a 22cm pie dish or spring-form pan with baking paper.
Crush biscuits to a fine crumb either in a food processor or by placing in a sealed bag and crushing with a rolling pin. Stir through melted butter/coconut oil and a pinch of salt.
Press base mix into prepared pan, using the bottom of a measuring cup or glass to press evenly on the bottom and 2cm up the sides. Place in freezer to set for 30 minutes.
Melt chocolate in a heat-proof bowl in the microwave, for 30 seconds at a time, stirring in between.
Place tofu, oat milk, espresso, nut butter and melted chocolate in a food processor and blend until completely smooth.
Pour filling onto base and allow to set in the freezer for 2-4 hours.
To serve, sprinkle pie with flaky sea salt and use a hot knife to slice through.