Mix the soy milk and flaxseed. Mix the flour, baking powder, salt and cocoa together. Mix together the oil and sugar, add the soy milk, flaxseed mixture and vanilla sugar. Gradually add the flour mixture. If it gets too dry, keep kneading with your hands. Add the hazelnuts and chocolate chips and knead the dough with your hands. Shape the dough into a roll and cut about 2.5 cm thick slices with a knife. Shape the biscuits nicely and spread them on a baking sheet. Bake at 180 ° C for about 10 minutes, let cool down on the baking sheet for 5 minutes and then let cool down completely on a wire rack.