Grilled Dark Chocolate Sandwich

1/4 cup fat-free evaporated milk
3 ounces bittersweet chocolate, finely chopped
1 1/2 tablespoons butter, softened
8 slices thin whole-wheat or white sandwich bread
3 tablespoons bittersweet or semisweet chocolate chips
2 tablespoons chopped toasted hazelnuts, (optional)

Heat evaporated milk just until boiling. Add chocolate, let stand for 1 minute, then whisk until smooth. Let cool slightly.

Spread butter on one side of each slice of bread. Divide the chocolate mixture on the unbuttered side of 4 slices, leaving a little border. Press chocolate chips and nuts, if using, into the chocolate. Cover with the remaining slices of bread, buttered-side up, and press lightly.

Cook the sandwiches in a large nonstick skillet over medium-high heat for 1 to 2 minutes. Turn over, press with a spatula, and cook until nicely browned and the chocolate is barely melted, 30 seconds to 1 minute.

Serve warm.