Preheat oven to 350F (180).

Line an 8 inch square baking dish with parchment paper.

Chop up the chocolate into small pieces.

Place butter and chocolate in a medium heatproof bowl over a pan of simmering water and stir until almost melted.

Remove from heat and stir until completely melted.

Add sugar and salt; whisk until smooth. Add vanilla and espresso and mix well.

Whisk in the eggs, one by one until just combined.

Fold in the flour with a spatula until smooth. Do not overmix.

Pour half of the brownie batter into the baking dish, spreading it evenly to the edges. Pour the salted caramel sauce over the batter, but leave out the edges. Save some salted caramel sauce for later.

Spoon the rest of the brownie batter over the caramel.

Bake for 40 minutes or until a toothpick inserted in the center comes out with a few moist crumbs. Do not over bake, otherwise your brownies will be dry.

Remove from the oven and allow to cool down completely (2 -3 hours).

Cut into 9 squares and serve with the rest of the salted caramel sauce.