Preheat the oven to 325°. Line a cupcake pan with cupcake liners and set aside.
In a large bowl, whisk together the oil, coffee, eggs, and vanilla until combined.
In a medium bowl sift together the flour, sugar, cocoa powder, baking soda, baking powder and salt. Add the dry ingredients to the wet and whisk together until fully combined.
Scoop the batter into the prepared cupcake pan until each liner is filled 2/3 of the way full. Bake for 18-22 minutes, or until the cupcakes spring back when lightly pressed in the center. Cool completely before frosting.
In the bowl of a mixer, add the butter and beat with the paddle attachment until smooth and pale. Add the powdered sugar and mix on low until the powdered sugar is starting to make a thick frosting with the butter.
Speed the mixer up and beat the buttercream until all the powdered has been absorbed into the butter. Add the vanilla and 2 tablespoons of milk. Beat until smooth, adding more milk as needed to get the buttercream to a smooth, pipeable frosting. Add the yellow food coloring and mix until you have a nice, even yellow buttercream.
Use a large round piping tip to pipe a large, even dollop of frosting on top of each cupcake.
Pour the red sprinkles into a shallow dish and press the bottom edge of the frosting into the sprinkles until the circumference of the cupcake.
Press one unwrapped truffle into the center of the cupcake. Use a lighter to gently heat the truffle just enough to press two chocolate melting wafers into the sides of the truffles, so that it resembles a Mickey Mouse head. Repeat until all the cupcakes are frosted and topped with a truffle Mickey.