Break up the chocolate and melt using a double boiler. Crush the biscuits into a fine powder. I find this is easy to do through the bag. Combine the crushed biscuits with melted butter and spread evenly in a mold lined with parchment paper. Chill in the fridge. Use a board to flatten.
Preheat the oven to 355°F/180°C. Beat the egg well.
Make the fillings. Whisk the cream cheese well. Then add other ingredients in order and mix well after each addition.
Pour half of Step 5 plus 10 g (total about 115 g) into a mold. Tap the mold against your work space to even the surface. Bake for 15 minutes at 355°F/180°C.
During baking, pour the rest of filling into a chocolate bowl and mix.
Sprinkle cocoa powder and add condensed milk. Then mix well again.
Pour the mixture into the mold. Tap and bake another 25 minutes at 340°F/170°C. I cover the top with aluminum foil.
It's done. Let it cool, wrap it up, and chill in the fridge. Leave for a half day. Slice and serve.
Here's the recipe doubled. I baked it in a 18 cm square mold. It's browned and baked without aluminium foil.
Story Behind this Recipe
This is a sister recipe of my strawberry cheesecake.
I use 20 g sugar, 30 g egg, and 5g condensed milk. Heavy cream is 47% fat, but 35% is also fine. For a simple taste, use 30 g of yogurt and 72 g cream cheese instead. After baking, the edge of the cake pops up, so it's better to slice it into 4 for bars.