Preheat the oven to 170C/ 325/ GM 3 then grease & line the bottom and sides of a deep 7-inch loose-bottomed baking tin with baking parchment. The neater you can line the tin, the neater the shape of the cheesecake will be once baked
Crush the biscuits: either pulse in a food processor or put into a plastic bag and bash with a rolling pin until they resemble breadcrumbs
Melt the butter in a small saucepan and tip in the crushed biscuits. Stir until thoroughly combined, then pour out into the baking tin and flatten across the bottom. Press down firmly using the back of a metal spoon and bake for 10 minutes. Set aside
Put the cream cheese into a medium-sized mixing bowl and beat with a balloon whisk until smooth
Pass the feta cheese through a medium fine-mesh sieve, using the back of a spoon to force it through. Doing this will ensure it is more easily and smoothly blended into the cheesecake
Beat the feta into the cream cheese, followed by the sugar. Continue to whisk until the mixture is nice and smooth again
Once the blackberry coulis is cool, reserve 1 tablespoon and pour the rest into the cheesecake batter along with the vanilla extract. Beat until incorporated Add the eggs and yolks. Continue to whisk until the mixture is nice and smooth again but do not over mix it
Pour the cheesecake batter carefully over the top of the biscuit base and bake for 35-40 minutes until the internal temperature of the cheesecake reaches 65C/ 149F. If you do not have a food thermometer, bake until the cheesecake is firm around the edges but the centre still has a good wobble and is not set completely
Remove from the oven and let cool completely. Cover and refrigerate for at least 4 hours to allow the cheesecake to set
Just before serving, whip the cream until it just holds its shape and use to pipe 12 rosettes around the edge of the cheesecake. Top each with a small drizzle of the reserved coulis and a fresh blackberry. Scatter the almond flakes into the centre of the cheesecake and dredge with a little icing sugar. Serve