1. Preheat oven to 350ºF. Line an 8-inch baking pan with foil so it overhangs 2 sides by 1 inch. In a bowl, mix flour, baking powder and salt.
2. Melt butter and chocolate in a bowl set over a pan of simmering water, stirring occasionally. Remove bowl from heat; let cool slightly.
3. In a separate bowl, whisk sugar and eggs. Stir in chocolate mixture and vanilla, then flour mixture. Transfer batter to pan. Set Almond Joy bars on top, pressing lightly.
4. Bake until just set, about 35 minutes. Let cool completely on wire rack.