Mix the flour with the starch, knead with the other ingredients to form a smooth dough, cover and chill for 30 minutes.
Preheat the oven to 175 ° C top / bottom heat.
Roll out the dough on one half of a greased baking sheet, brush with jam.
Caramelize the sugar and vanilla sugar in a pan, stir in the nuts. Add butter and stir until the sugar has dissolved, deglaze with 2 tablespoons of water and cream and caramelize until golden brown. Spread the mixture on the dough.
Bake in the hot oven on the lowest rack for about 15 minutes. Let cool and divide into squares.