Step 1

Preheat the oven to 325ºF and lightly grease a 9x9 inch metal baking pan.

Step 2

In a large bowl, whisk together the almond flour, sweetener, cocoa powder, baking powder, espresso powder, and salt.

Step 3

Add the eggs, oil, zucchini, and vanilla extract and stir until well combined. Stir in about 1/3 cup of the chopped walnuts, if using.

Step 4

Spread the mixture in the pan and sprinkle with the remaining chopped walnuts. Bake 18 to 25 minutes, or until the brownies are puffed on top and just firm to the touch.

Step 5

Remove and let cool completely in the pan.

Step 6

In a medium bowl, beat the butter and cream cheese together until very smooth. Beat in the cocoa powder and sweetener.

Step 7

Add the heavy cream a little at a time, beating after each addition. Beat in the vanilla extract, and more cream as needed to achieve a spreadable consistency.

Step 8

Spread over the cooled brownies and refrigerate 30 minutes to help firm up both the brownies and the frosting before cutting into bars.