Preheat your oven to 320°F/160°C. Line a 9-inch square pan with parchment paper.
In a small pot, melt the butter. Add the biscuit crumbs and mix until combined. Pack it into the pan and put it in the refrigerator to cool.
In a large bowl, use a whisk to beat together the cream cheese and sour cream until smooth. Stir in the sugar until combined. Add the eggs and egg yolks one at a time. Then add the heavy cream and vanilla. Use a spatula to fold in the corn starch and flour.
Pour the filling into the pan and bake for 40 minutes. Let it come to room temperature before putting it in the refrigerator to set overnight.