- Preheat the oven to 350°F. Lightly spray three 9-inch cake pans with cooking spray or grease them with a bit of butter.
- To make the cake : Combine the milk and vinegar in a medium bowl. Set aside.
- Whisk together the rice flour, cocoa powder, oat flour, sugar, baking powder, baking soda, and salt in a large bowl.
- Add the maple syrup, butter, aquafaba, and vanilla to the milk mixture and whisk until combined. Add the wet ingredients to the dry ingredients and stir until thoroughly combined and smooth.
- Distribute the batter evenly among the three pans. Bake for 35 to 40 minutes, until a toothpick inserted into the center comes out clean.
- Let the layers cool in the pans for about 30 minutes. Run a knife around the inside edge of the cake pans and gently transfer the layers to cooling racks to let them cool completely.
- Once the layers come out of the oven, make the frosting : Melt the chocolate chips in a double boiler or a heatproof bowl on top a pot of boiling water, stirring occasionally, until smooth. Remove from the heat. Combine the dates and milk in a food process
- Add the melted chocolate, cocoa powder, vanilla, and salt and process until smooth. Transfer the frosting to a jar and refrigerate for at least 30 minutes, or until ready to use.
- Once the frosting has chilled and thickened, place one of the layers on a plate or serving dish. Using a thin silicone spatula or a butter knife, evenly spread a layer of frosting on top. Place another layer on top of the frosting.
- Evenly spread frosting on the top of the second layer, then top with the third layer. Spread the rest of the frosting evenly over the top and around the sides until the entire cake is covered. Top with chocolate shavings, if desired.
- Slice and serve. The cake will keep, covered, at room temperature or in the fridge for 3 to 4 days.
- VARIATION To make 12 cupcakes, divide the quantity of the cake ingredients by three and the frosting ingredients by two. Line the cups of a 12-cup muffin tin with paper or silicone liners and distribute the batter evenly among the cups.
- Bake for 18 to 20 minutes, until a toothpick inserted into the center comes out almost clean. Let the cupcakes cool in the tin for 30 minutes before transferring them to the cooling rack. Cool completely before frosting.
