Make the cake.  Preheat oven to 350 degrees F/ 325 degrees F convection.  Oil a 9 inch cake pan.  In a large microwave safe bowl, melt coconut oil and carob or chocolate on high in 30 second increments, stirring in between, until fully melted.  Stir in the espresso powder, sugar, vanilla, and eggs.  Stir in half the flour, followed by the milk, then the remaining flour along with carob or cocoa powder, and salt.

Pour batter into the prepared pan, and bake about 30-45 minutes, until a toothpick inserted in the center comes out clean or with a few crumbs.  Cool completely in the pan.

Make the frosting.  In a medium microwave safe bowl, place carob or cocoa powder, milk, carob or dark chocolate chips, and espresso powder.  Microwave on high in 30 second increments, stirring in between, until fully melted.  Stir in the coconut butter, vanilla, and as much additional milk as needed for a spreadable consistency.

Spread onto the cake, slice, and serve.  Cake may be stored in an airtight container at room temperature for up to 3 days, or frozen, wrapped in parchment and foil, and placed in a zipper bag for up to 3 months.  Thaw in the microwave about 1 minute.