About two dozen cutout sugar cookies with colored hard-candy windows.

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Cream 3/4 cup butter with 3/4 cup sugar, then mix in one egg and 1 tsp vanilla. Whisk 2 1/2 cups flour with 1/2 tsp baking powder and 1/4 tsp salt; mix in just until a dough forms. Flatten into two disks and chill at least 60 minutes.
Heat oven to 350°F. Roll one disk at a time to roughly 1/4 inch between parchment. Cut about 24 shapes with a 2 1/2-inch cutter, rerolling scraps gently, then remove a 1-inch window from each. Transfer spaced cutouts to parchment-lined sheets. Crush unwrapped candies by color.
Fill each cutout window with a thin, even layer of the measured 1/2 cup crushed candy, keeping shards off dough edges. Bake one tray at a time approximately 10–12 minutes until dough edges set and candy melts into a smooth center without bubbling over.
Leave cookies on parchment on their sheets until candy windows are completely hard, about 30 minutes after the final tray. Peel away carefully. Record actual shape count, candy allocation and whether windows detach in a kitchen trial.

Recipe-development draft; not kitchen-tested. Timing and yield are estimates. Nutrition has not been calculated.

Additional chilling, resting or cooling time: 90 minutes, included in the total.

Untested estimate: chill 60 minutes, bake two trays about 12 minutes each, cool last tray 30 minutes on parchment; preheat excluded.