Heat the oven to 350°F and line an 8-inch square pan with parchment.
Whisk flour, cocoa, and salt in a bowl.
Whisk melted butter, sugar, eggs, vanilla, and half of the coffee until smooth. Fold in the dry ingredients, spread in the pan, and bake 25 to 28 minutes until the center has moist crumbs.
Cool the brownies completely in the pan.
Melt the chocolate with the remaining coffee over a gentle double boiler, then cool until barely warm.
Whip the cream with powdered sugar to soft peaks. Fold in the cooled chocolate mixture.
Spread the mocha mousse over the brownies, top with raspberries, and chill at least 3 hours.
Lift out, slice into 16 squares, and serve cold.