Preheat the oven to 350 degrees Farenheit.

Lightly butter the inside of a bundt pan and then dust the inside of the pan with a fine layer of granulated sugar. Tap out any excess. Set aside.

In a small mixing bowl, whisk together the flour and baking powder. Set aside.

Put the butter and sugar in the bowl of a stand mixer fitted with the paddle attachment (or use a large mixing bowl and an electric handheld mixer).

Beat the butter and sugar on medium speed for about 3-4 minutes, until light and fluffy.

Add the eggs and vanilla and beat well.

Reduce the mixer to low speed and gradually add in the flour and baking powder mixture until well combined. The dough will be a thick batter.

Remove approximately one third of the dough to another mixing bowl.

Add the cocoa powder, espresso powder if using, and hot water to a small bowl and whisk well. Add the cocoa mixture to the mixing bowl with the smaller portion of the dough. Mix with a spatula until fully combined.

To the mixing bowl with the larger portion of dough, add the orange juice and orange zest and mix with a spatula until fully combined.

Spread half of the orange dough over the bottom of the bundt pan. Scoop the chocolate dough on top of that and gently even it out with a spoon or spatula, then top with the rest of the orange dough. Even gently again.

I like to gently drag a butter knife through the dough a few times to help create the stripes.

Bake for 47-55 minutes, until cooked through. It will be browned on top and should be gently pulling away from the edges. A toothpick inserted in the middle should come out clean.

Let the cake cool in the pan for 10 minutes, then gently invert onto a plate or cake stand. Allow to cool fully.

For the ganache, place the chocolate chips in a small bowl. Heat the heavy cream to just below a simmer, then pour over the chips. Allow to sit for a minute, then whisk well.

Use a spoon or small ladle to scoop the ganache over the cake.