COMBINE flour, sugar, baking powder and salt in large bowl.
MICROWAVE morsels and butter in medium, uncovered, microwave-safe bowl on HIGH (100%) power for 1 minute; STIR. The morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until melted. Cool to room temperature. Stir in milk, eggs and vanilla extract. Add chocolate mixture to flour mixture; stir (batter will be thick).
COOK in Belgian waffle maker* according to manufacturer's directions. Serve warm with your choice of toppings.
* Can also be cooked in standard waffle maker (makes about 20 standard-size waffle squares).