1. Preheat your conventional oven to 175°C.
Grease and flour one 8-inch-diameter cake pan.
2. Whisk the sugar, sour cream, olive oil, egg, and vanilla in a large bowl to combine.
3. Sift in flour, cocoa, and baking soda, then use a spatula and stir to mix thoroughly.
Pour the batter into the greased and floured pan, then place in the oven and bake for 25 minutes (until a toothpick inserted into the center comes out clean).
4. Cool in the pan on a rack for 10 minutes.
Turn the cake out onto the rack and let it cool completely. Turn the oven down to 65°C.
5. Once the cake has cooled, divide it into thirds.
In a large bowl, gently crumble two-thirds of the cake and reserve, covered, until ready to use. The crumbs will be moist and quite large.
6. Crumble the remaining cake into moist crumbs and place them on a lined baking sheet in an oven preheated to 65°C for 2 hours (or until sandy to the touch).
Pulse in a food processor or blender and keep in a sealed container until ready to use. They will have a lighter, drier texture.
