Place chocolate squares between 2 white bread slices; brush both sides of sandwich with 1 1/2 tsp. melted butter. Cook in a hot nonstick skillet over medium-high heat 30 to 60 seconds on each side or until chocolate is melted and bread is golden brown. Dust with powdered sugar. Garnish with raspberries, if desired.
Cut bread into heart or other desired shape before filling with chocolate and cooking.
For testing purposes, we used thin squares that would melt quickly and evenly, such as Ghirardelli 60% Cacao SQUARES Dark Chocolate, Ghirardelli Milk Chocolate With Caramelized Almonds SQUARES, and Lindt Excellence 70% Cocoa Dark Chocolate Extra Fine Squares.
Other good fillings include raspberry jam, marshmallow cream, toasted pecans, peanut butter, and sliced bananas.