Start by preheating your oven to 350°F. Grease a 9-inch cake pan and line the bottom with parchment paper if possible.

I learned the hard way that chocolate cakes can sometimes stick, even when you think you've greased the pan enough. The parchment gives a little insurance policy and makes removing the cake much easier.

Wash and dry the zucchini. Trim off the ends and grate it using the large holes of a box grater.

You don't need to peel the zucchini. The skin softens during baking and blends right into the cake. Don't squeeze all the moisture out either. That moisture is part of what makes this cake so soft.

Set the grated zucchini aside while you prepare the batter.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.

Take a minute to break up any cocoa powder lumps. I skipped this step once and ended up with little pockets of cocoa in the finished cake. It wasn't terrible, but it wasn't ideal either.

The mixture should look evenly blended with a rich brown color.

In a large mixing bowl, combine the granulated sugar, brown sugar, eggs, vegetable oil, and vanilla extract.

Whisk until the mixture becomes smooth and slightly lighter in color. This usually takes about two minutes.

Pour in the melted chocolate and stir until fully incorporated. The batter will begin looking glossy and chocolate-rich at this point.

Gradually add the dry ingredients to the wet mixture.

Use a spatula or wooden spoon and mix just until combined. Try not to overwork the batter.

At first it may seem slightly thick, but that's normal.

Add the grated zucchini and gently fold it into the batter.

This is where the texture changes. As the zucchini releases moisture, the batter becomes easier to stir and slightly looser.

Make sure the zucchini is evenly distributed throughout the mixture.

Pour the batter into the prepared pan and smooth the top.

Bake for 38 to 42 minutes.

Around the 30-minute mark, your kitchen will start smelling deeply chocolatey. The top should look set and slightly springy when lightly touched.

Insert a toothpick into the center. A few moist crumbs are fine, but you shouldn't see wet batter.

Remove the cake from the oven and allow it to cool in the pan for 15 minutes before transferring it to a wire rack.

Place the chocolate, butter, and milk in a small pot over low heat.

Stir continuously until everything melts together into a smooth mixture.

Remove from the heat and gradually whisk in the powdered sugar until smooth.

Let the frosting cool slightly. It should thicken enough to spread easily without running down the sides.

Once the cake is completely cool, spread the frosting evenly over the top.

Use the back of a spoon to create simple swirls if you'd like.

I rarely worry about making it look perfect. A homemade cake should look homemade.

Allow the frosting to set for about 15 minutes before slicing.

The cake cuts cleanly and reveals a soft, moist interior with a rich chocolate color.