Sure, the zucchini in this cake adds some nutritional value, but more important, it lends a wonderful soft texture to the crumb. The poppy seeds add some crunch, and the chopped chocolate ensures it doesn’t taste too wholesome. I think this cake is great on its own, but if you’d like to add a topping, I suggest the Cocoa Glaze (see below).
¾ cup (150g) sugar
2 large eggs
¾ cup (180 ml) neutral oil, like canola or grapeseed
1 tablespoon poppy seeds (optional)
½ teaspoon cardamom
¼ teaspoon cinnamon
¾ teaspoon kosher salt
½ cup (45g) unsweetened Dutch-process cocoa powder
1 ¼ cups (160g) all-purpose flour
½ teaspoon baking powder
½ teaspoon baking soda
2 ¼ cups (225g) grated zucchini (use large holes of a box grater), squeezed to remove excess moisture
¾ cup (128g) chopped bittersweet or semisweet chocolate or chocolate chips
Position a rack in the center of your oven and preheat the oven to 350°F. Butter or coat an 8-inch square baking pan with nonstick spray. Line the pan with a strip of parchment paper that hangs over two of the edges.
In a large bowl, whisk the sugar and eggs until pale and foamy, about 1 minute. Add the oil, poppy seeds (if using), cardamom, cinnamon, and salt. Whisk until smooth and emulsified. Add the cocoa powder and whisk until smooth.
Add the flour, baking powder, and baking soda and stir until well-combined and smooth. Use a rubber spatula to fold in the grated zucchini and ½ cup (85g) of the chocolate.
Pour the batter into the prepared pan, tap the pan gently on the counter to release any air bubbles, and smooth the top of the batter with an offset spatula. Sprinkle the remaining ¼ cup (42g) chocolate over the top of the cake.
Bake the cake until puffed and a tester inserted into the center comes out clean, 35 to 45 minutes. Set the pan on a rack to cool for about 15 minutes. Then use the parchment paper to lift the cake out of the pan and set it on the rack to cool completely. (Store the cake, well wrapped, at room temperature for up to three days.)
1 cup (100g) confectioners’ sugar
3 tablespoons unsweetened Dutch-process cocoa powder
1 tablespoon unsalted butter, very soft
Pinch of salt
2 to 3 tablespoons boiling water
Make the glaze: Add the confectioners’ sugar and cocoa to a bowl. Whisk until combined and any lumps in the cocoa have been broken up. Add the butter, salt, and 2 tablespoons boiling water and quickly whisk until smooth; if the glaze is very thick, add a few drops of water until it has a smooth and pourable consistency.
Immediately pour the glaze over the cooled cake (the glaze will harden to a more spreadable rather than pourable consistency if you let it sit). Let the glaze set for about 20 minutes before slicing the cake. (Store the cake, covered, at room temperature or in the fridge for up to three days.)