Add the ingredients to a bowl and knead everything with your hands until a smooth dough forms. Cover the bowl with plastic wrap and refrigerate for 30 minutes.
Preheat the oven to 325°F. Line a sheet pan with parchment paper and evenly spread the dough over it.
Spread the apricot jam evenly over the dough.
Put the hazelnuts in a freezer bag or tea towel and crush them with a rolling pin, pot, or pan to get small pieces.
Heat the butter in a saucepan over medium heat, add the sugar, vanilla extract, and water and bring everything to a boil. Add the crushed hazelnuts to the saucepan and mix well.
Spread the hazelnut topping over the apricot jam layer on the dough, put the pan in the oven, and cook for 30 minutes.
Once the pastry has cooled down, cut it into 24 equal triangles.
Add the milk chocolate and dark chocolate to a glass bowl and melt over a water bath. Add 2 tablespoons of oil and stir well. Dip the 2 short sides of the hazelnut triangles into the melted chocolate and lay on a piece of parchment paper to dry.