In large bowl cream butter and sugar until light and fluffy; beat in egg, chocolate and vanilla. In medium bowl combine flour, baking powder and salt; add to creamed mixture. Wrap and refrigerate dough 2 to 3 hours. Preheat oven to 350°F. Working with half the dough at a time on lightly floured surface, roll to 1/4-inch thickness. Cut into dinosaur shapes using 4-inch cookie cutters. Place about 2 inches apart on ungreased cookie sheets. Bake 10 to 12 minutes. Cool 2 minutes on cookie sheets; cool completely on wire racks. Tint frosting to desired colors. Frost cookies and decorate with "M&M’s"® Chocolate Mini Baking Bits. Store in tightly covered container.