1. In a 3- to 4-quart pan over medium-high heat, melt butter, stirring occasionally, about 4 minutes. Remove from heat.
2. Stir in sugar, then eggs and vanilla, until blended. Stir in salt and baking powder. Add flour and cocoa and stir until batter is smooth.
3. Butter a 12- by 20-inch piece of foil. Line a 9- by 13-inch pan with foil, buttered side up, letting foil hang over pan ends. Scrape batter into pan. Evenly space caramels over batter.
4. Bake brownies in a 325° oven just until a toothpick inserted in the center (not in a caramel) comes out clean, 55 to 60 minutes. Let cool.
5. Lift brownies with foil from pan to a counter. Peel back sides of foil. With a long, hot knife, cut between caramels into 35 squares; occasionally rinse knife in very hot water and wipe clean.