In a bowl, mix the eggs, sugar, and vanilla sugar. Then, add the oil, melted butter, salt, and baking powder. Mix everything together, and slowly add the flour. Continue mixing until a soft dough forms.
Take out approximately 1/4 of the dough (or a little less) to use for the topping later.
Brush a tray with butter or oil to prevent the dough from sticking.
Flatten the dough evenly in the prepared tray, making sure it covers the bottom completely.
Top the flattened dough with your choice of jam, spreading it evenly over the surface.
Shred the reserved portion of the dough on top of the jam, creating a crumbly topping.
Bake the dough at 360°F for about 30 minutes, or until it turns golden brown.
Remove the tray from the oven and let it cool. Once cooled, cut the dessert into squares.
Store the squares in a tightly closed container on the counter for up to 1 week, in the fridge for up to 1 month, or in the freezer for up to 6 months.