Cream butter, powdered sugar, vanilla sugar, and salt until light and fluffy. Add eggs one at a time. Gradually mix in flour and baking powder until smooth. Divide dough into 3 equal portions.

Mix one portion of dough with ground pistachios and lemon zest. Roll out to ½ cm thick, cut into shapes, and place on a lined baking sheet.

Fold in cocoa powder to the second dough portion. Shape into small balls and roll into sticks approximately 8 cm long. Place on a lined baking sheet.

Roll the last dough portion into balls, dip in egg white, and roll in chopped peanuts. Flatten slightly and press thumb into each ball.

Combine strawberry jam and granulated sugar in a saucepan, stir over medium heat until bubbling and thick. Cool before filling thumbprint cookies.

Preheat oven to 190 °C (375 °F). Bake cookies for 10-15 minutes until edges are lightly golden.

Dip half of pistachio-lemon cookies in melted white chocolate, garnish with chopped pistachios. Dip chocolate sticks in melted milk chocolate and sprinkle with crushed hazelnuts.