Hazelnut bundt cake - Moje wypieki

Ingredients

• 250 g butter
• 125 ml water
• 1 cup sugar
• 1 packet vanillin sugar (16 g)
• 1 cup plain flour
• 1 cup ground hazelnuts (or other nuts)
• 2 tablespoons cocoa powder
• 3 teaspoons baking powder
• 4 eggs, separated
• 50 g chopped hazelnuts (or other nuts)