Step 1

Preheat your oven to 350°F. Lightly grease a 9" square pan.

Step 2

, To make the brownies: Combine the zucchini, melted butter, eggs, and vanilla in the work bowl of a food processor, and process until smooth.

Step 3

, Add the sugar, cocoa powder, espresso powder, baking powder, salt, and flour; process briefly, just until well combined.

Step 4

, Add the chips and pulse several times, to break them up just a bit.

Step 5

, Pour the batter into the prepared pan.

Step 6

, Bake the brownies for 28 to 32 minutes, until a toothpick inserted into the center comes out clean, or with a few moist crumbs clinging to it; you shouldn't see any sign of wet batter. Remove the brownies from the oven, and allow them to cool completely before frosting.

Step 7

, To make the frosting: Combine the chocolate chips and milk or cream in a microwave-safe bowl or small saucepan. Heat until the milk is steaming and the chips are soft. Remove from the heat and stir until smooth.

Step 8

, Spread the frosting atop the brownies. Place them in the refrigerator for an hour or so, to set; then store them at room temperature, covered, for several days.