Preheat the oven to 180 degrees (convection 160 degrees).
Melt the chocolate in a water bath and let it cool down a little. Stir the oil into the chocolate. Beat the eggs with the mixer on the highest setting until foamy, slowly drizzling in the sugar. Beat until the sugar has dissolved and a thick, creamy mixture has formed. Add the vanilla flavor. Mix the flour, salt and baking powder together. Add the chocolate mixture to the foam mass and stir briefly, then add the flour and carefully stir in with a wooden spoon.
Place the dough on a greased baking sheet and smooth it out with a spoon. Bake for 20-25 minutes. After cooling, cut into squares.