In a large bowl, cream butter and cream cheese. Beat in flour. Refrigerate, covered, 30 minutes or until easy to handle., Preheat oven to 350°. Spread hazelnuts in a 15x10x1-in. baking pan. Bake 7-10 minutes or until fragrant and lightly browned, stirring occasionally. To remove skins, wrap hazelnuts in a tea towel; rub with towel to loosen skins. Reserve 24 hazelnuts for topping., Shape dough into 24 balls. With floured fingers, press evenly onto bottom and up the sides of ungreased mini-muffin cups., Place brown sugar and remaining hazelnuts in a food processor; pulse until hazelnuts are finely ground. In a small bowl, whisk egg, melted butter and vanilla; stir in hazelnut mixture. Fill cups with 2 teaspoons; top each with a reserved hazelnut., Bake 18-22 minutes or until set. Remove to wire racks to cool.