Preheat the oven to 350° F and line your muffin pan with paper liners.
In a large bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt.
In a small bowl, mix the oil, sugar, flax-water mixture, vanilla, and soy milk together until well combined. Pour the wet ingredients into the dry ingredients, add the hot water, and mix again until well combined.
Spoon the batter into the lined cupcake pan, filling each cup about ⅔ full. Bake for 20 to 22 minutes, or until a toothpick inserted in the center comes out clean. Let them cool in the pan for 10 to 15 minutes, then you can remove them to a plate or cooling rack. Cool the cupcakes completely before frosting, or the frosting can melt. If you want to cool them faster after removing from the pan, you can stick them into the freezer for about 20 minutes.
Make the frosting while the cupcakes bake and cool.
Use a fork or a hand mixer to cream the butter.
Add the remaining ingredients, and beat with your fork or mixer until you have a light, fluffy frosting.
If your frosting is too thin, add more powdered sugar by the tablespoon, beating between additions, until it thickens up. Too thick? Add vegan milk by the tablespoon, beating between additions, until it's nice and fluffy.
Assemble the cupcakes.
Use a knife at an angle to cut a small, cone-shaped piece out of the top of each cupcake. Set those cones aside - you'll need them! Use a small spoon or a piping bag to fill the hole with the peanut butter frosting. Then, remove the pointy parts of the cones, and stick them back on top of each cupcake to "cap" the frosting-filled holes you cut out.
Top the cupcakes with your toppings of choice!
Video
Notes
Nutritional information doesn't include toppings.The peanut butter you choose can make or break this recipe. If it separates at room temperature, then don't use it for this frosting.Make sure the vegan butter is softened before making the frosting, so it will whip up easily into a light, fluffy frosting.You can make the cupcakes up to a day or two ahead, but don't frost them until day-of, so they'll have the best texture when you serve them!. Store the cooled, unfilled cupcakes in a container lined with a paper towel until you're ready to frost. You can make the frosting in advance as well, just whip it up again before using.Frosted cupcakes will keep for 1 to 2 days in a closed container on the kitchen counter.You can also make the cupcakes and freeze them (unfilled) for up to three months. Thaw them overnight in the refrigerator or for a few hours on the kitchen counter before frosting and serving.