In a large bowl, whisk together flour, cocoa powder, and baking soda.
In a small bowl, whisk together dairy-free milk, sugar, oil, vinegar, and vanilla.
Transfer wet ingredients to large bowl with dry ingredients, and stir to combine.
Fill each muffin cup half full and bake for about 15-20 minutes.
Once cooked through, remove from oven and let cool for 10 minutes, then transfer to wire racks to let cool completely.
To make frosting, beat softened dairy-free butter using a stand mixer or hand mixer. Add powdered sugar and vanilla and continue to beat until silky smooth frosting comes together. Decorate and enjoy!