5 tablespoons unsalted butter, plus extra at room temperature for greasing the pan
1 tablespoon instant espresso powder
1 1/2 cups all-purpose flour, spooned and leveled
1 teaspoon baking soda
1/4 teaspoon kosher salt
4 medium-ripe bananas (the peel should be pretty black), peeled and halved
1/2 cup granulated sugar
2 tablespoons lightly-packed light brown sugar
1 large egg, beaten
3 ounces semisweet chocolate, finely chopped
1 1/2 sticks (12 tablespoons) unsalted butter, at room temperature
2 tablespoons confectioners' sugar
1 teaspoon instant espresso powder
Pinch of ground cinnamon
Pinch of fine salt