Start by getting your cake pans ready. Set your oven to 350°F (175°C). Grease two 8-inch round cake pans, put a piece of parchment paper on the bottom of each, then lightly dust them with cocoa powder. This helps prevent sticking and adds a little extra flavor.

Next, in a big bowl, mix together your dry ingredients: flour, cocoa powder, baking powder, baking soda, and salt. Give it a good whisk so everything is evenly combined, then set it aside.

In another bowl, beat the eggs with both the brown and white sugar. Keep beating for a couple of minutes until the mixture turns light and fluffy. Then add the oil, vanilla extract, orange juice, orange zest, sour cream, and milk. Stir everything together until smooth and well mixed.

Now combine the wet and dry ingredients. Slowly add the dry mixture into the wet, a little at a time. Stir gently, just until everything is mixed—don’t overdo it, or the cake might turn out dense.

Pour the batter evenly into the two prepared pans. Bake them for about 30 to 35 minutes. You’ll know they’re done when a toothpick poked into the center comes out clean. Let the cakes cool in the pans for 10 minutes before taking them out and placing them on a wire rack to cool completely.

While the cakes are cooling, make the chocolate orange ganache. Heat the heavy cream in a small pot until it just starts to simmer don’t let it boil. Pour the hot cream over chopped chocolate in a heatproof bowl. Let it sit for a few minutes, then stir until smooth.

Add orange zest, a bit of butter, and orange liqueur if you want. Stir again until it’s glossy. Let it cool until it thickens enough to spread this usually takes 15 to 20 minutes at room temperature, or you can pop it in the fridge and stir it now and then to speed it up.

To put the cake together, make sure the layers are even by trimming the tops if needed. Place the first cake layer on a serving plate and spread some ganache on top.

Add the second cake layer and cover the whole cake with more ganache top and sides. Use a spatula to smooth it out. You can decorate the cake however you like candied orange slices, chocolate curls, or a bit of orange zest on top all work nicely.