Heat the oven to 350 degrees F.
Line a 9-by-13-inch pan with parchment paper.
Whisk melted butter, granulated sugar, and brown sugar until smooth.
Add eggs and vanilla.
Whisk until the mixture looks glossy.
Stir in flour, cocoa powder, espresso powder, and salt.
Fold in chocolate chips.
Spread the batter evenly in the pan.
Bake for 30 to 35 minutes, until moist crumbs cling to a toothpick.
Cool the brownies in the pan for 20 minutes before adding fudge.
Melt chocolate chips, condensed milk, butter, cream, and salt in a small saucepan.
Stir over low heat until smooth.
Remove from heat.
Add vanilla.
Pour warm fudge over the brownies.
Let the pan cool for 45 minutes before slicing.