Make the brownies: Preheat the oven to 350 degrees F. Lightly grease
a 12-by-16-inch half-sheet pan
with the softened butter and set aside. In a large bowl, whisk
together the eggs and sugar
to make a slurry
; set aside. Melt
the 1 1/2 sticks butter in a large saucepan
over medium heat. Stir in 1 cup of the chocolate chips
and cook, stirring often, until the chocolate is completely melted, then stir in the espresso powder. Transfer the chocolate-espresso mixture to the bowl with the egg slurry. Add the flour and baking soda and stir to combine. Pour the batter
into the prepared half-sheet pan and bake until glossy on the surface and still jiggles slightly when the pan is tapped, about 20 minutes. Remove from the oven and set aside to cool completely.
Make the topping: Increase the oven temperature to 400 degrees F. Place the pecans
on a rimmed baking sheet and toast for 5 minutes. Remove the pecans from the oven and transfer to a heat-safe plate. Combine the condensed milk, coconut
, vanilla, salt and pecans in a medium saucepan and cook over medium-low heat, stirring often, until the condensed milk is very thick and turns the color of caramel
, about 20 minutes. Set aside to cool slightly.
Cut the brownies into twelve 3-by-4-inch squares. Pour the warm topping over the brownies and serve while warm or when cooled.