1. Preheat oven to 350°F (175°C). Grease and line a 9-inch round cake pan or an 8×8-inch square pan with parchment.

2. In a large bowl, whisk flour, sugar, cocoa powder, baking soda, baking powder, and salt until evenly combined.

3. In a second bowl, whisk milk, melted coconut oil, eggs, vanilla, and hot coffee until smooth.

4. Whisk the sourdough discard into the wet mixture until fully incorporated.

5. Pour wet ingredients into dry ingredients. Whisk just until smooth and combined (batter will be thin).

6. Pour batter into the prepared pan. Bake 35–40 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.

7. Cool in the pan 10 minutes, then transfer to a wire rack to cool completely before frosting.

8. Make frosting: Beat butter until creamy. Add powdered sugar and cocoa powder in batches, mixing on low then increasing speed. Add vanilla and milk; beat until fluffy and spreadable (add 1 tsp more milk if needed).

9. Frost cooled cake, slice, and serve.