Preheat oven to 350 degrees.

Put unsweetened chocolate in a small bowl and microwave on high for 30 seconds. Stir; microwave for another 30 seconds. Stir again and continue microwaving in 10 second increments just until melted. Set aside to cool.

In a large mixing bowl, whisk together flour, baking powder, baking soda, cinnamon, nutmeg and salt. Set aside.

Using an electric stand mixer with the paddle attachment, beat butter on medium speed (3 to 4) until creamy. With the machine running, add granulated sugar. Continue beating until well combined, around 2 to 3 minutes. Beat in cooled melted chocolate. Beat in the eggs, one at a time. Beat in half and half, zest and 1 teaspoon of the vanilla.

Reduce machine speed to low (or “stir”) and add zucchini. Stop mixing but leave batter in bowl on machine (you’ll come back to it shortly).

Using nonstick cooking spray, grease and sugar a 10-inch (12 cup) Bundt pan (see Note below). Don’t use butter or flour; the cake’s more likely to stick to the pan with those.

Back to the batter: with the machine on low (“stir”), beat in flour mixture and chocolate chips just until blended. Spoon batter into prepared pan and bake for around 45 to 50 minutes, or until a wooden pick inserted in the middle comes out clean.

Remove cake from oven and gently run a knife around the edges (inside and out). Let sit in pan for 10 minutes.

Again, run a knife around the edges of the cake, and then turn over (upside down) onto a wire rack. Let sit for around 5 minutes – the cake should fall out of the pan onto the rack. If not, gently shake the pan a few times. If still not out, let sit for a few more minutes – it should fall out. Let cool completely.

In the top of a double boiler, stir together the bittersweet chocolate, cream, corn syrup, and remaining 1/2 teaspoon vanilla. Place over boiling water and cook, stirring constantly, until the chocolate is melted and the glaze is smooth. Remove from over water and set aside to cool and thicken slightly, for around 5 minutes.

Spoon glaze over the top of cake, letting it drip down the sides. (You might have some glaze left over.) Let the cake stand until glaze is set, around 20 to 30 minutes. You can also pop it in the refrigerator to get it to set faster.

Just before serving, dust top of cake with powdered sugar. If desired, serve with a scoop of ice cream.