Pre-heat your oven to 350℉.
Coarsely chop the chocolate and butter and melt them together in a double boiler or a bowl over a small pot of simmering water. Once nearly melted, remove the bowl from the heat and stir to combine. Set aside briefly to cool.
5 ounces (142 grams) bittersweet or semisweet chocolate, 4 ounces (1 stick, 113 grams) unsalted butter
Line an 8 or 9 inch square baking pan with parchment or aluminum foil, then lightly butter the parchment or foil. Set aside.
Whisk the dry ingredients (flour, cocoa, espresso powder, baking powder, and salt) together in a small bowl.
1 cup (125 grams) all-purpose flour, ¼ cup (20 grams) cocoa powder, 1 tablespoon espresso powder, ½ teaspoon baking powder, ¼ teaspoon salt
Combine the sugar and eggs in the bowl of your stand mixer (or in a large mixing bowl if using a hand mixer or beating by hand). Beat on medium speed until lightened, about 2 to 3 minutes.
1¼ cup (250 grams) granulated sugar, 2 large eggs
Add the vanilla extract and beat another minute.
1 teaspoon vanilla extract
Slowly beat in the melted chocolate and butter. Then add the dry ingredients and mix on low.
Stir in the chocolate chips by hand, then turn the espresso brownie batter out into your prepared pan. Use a spatula to get the brownie batter into the edges and corners of the baking pan, but don't worry about making it perfectly smooth.
½ cup semisweet or bittersweet chocolate chips
Bake the espresso brownies for 28 to 30 minutes until the top is slightly firm and a toothpick inserted into the center comes out clean. Make the salted caramel sauce while the brownies are baking.