Heat oven to 350°F. Line 13x9x2-inch baking pan with foil, extending foil over sides of pan. Grease bottom and sides of foiled-lined pan.
Melt butter in medium saucepan. Stir in sugar, flour, cocoa, baking powder, eggs, milk and 1-1/2 teaspoons vanilla extract; blend well. Stir in nuts. Spread batter in prepared pan.
Bake 40 minutes or until brownies begin to pull away from sides of pan. Just before brownies are done, melt chocolate chips with sweetened condensed milk and remaining 1-1/2 teaspoons vanilla. Immediately spread over hot brownie. Cool in pan on wire rack. Refrigerate just until fudge layer is set.
Using heart-shaped cookie cutters, cut out brownie hearts. Press each brownie heart out of cookie cutter so that fudge side is against wax paper. Turn over so that fudge side is on top.
Prepared and tint frosting to desired color or colors. Pipe messages or decorations onto fudge. Garnish with sugar and small candies as desired.