Preheat oven to 350°F and grease and line a 9-inch round cake pan

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

In a separate bowl, whisk together the sugars to get rid of any clumps. Then mix in the olive oil, eggs, buttermilk, and vanilla extract

Sift your dry ingredients into the bowl with your wet and mix until just combined. Gently mix in hot water

Pour batter into prepared cake pan and bake for 25-30 minutes, until a toothpick inserted into the center comes out with only a few moist crumbs

Cool the cake in the pan for 15 minutes, then invert onto a wire rack to cool completely

Place the chopped dark mint chocolate and butter in an even layer at the bottom of a heatproof bowl

Add your cream to a small pot and heat over medium-low on the stove until steaming and just starts to simmer. Don’t let it get too hot!

Pour the warm cream over your chocolate and cover your bowl for 5 minutes. Add salt and stir with a spatula until smooth and glossy. If it’s not smooth, heat in the microwave in 5-second intervals until all the chocolate and butter have melted

Leave to cool for 20 minutes, stirring occasionally. This will thicken it so you can pour the ganache over your cooled cake without it running off. Use a spatula to spread it to the edge

Let your ganache set for 30 minutes at room temperature before slicing