Preheat oven to 350 degrees and line pans with cupcake liners.
Prepare cake mix & bake according to the box's instructions. Let cool completely.
Meanwhile, make the frosting in a large mixing bowl (with a hand mixer) or the bowl of a stand mixer by beating the butter, vanilla and salt together for 1 minute. Add the powdered sugar and milk and beat for 1 minute, scrape down the sides, remove a ⅓ cup of the frosting and place in a small bowl. Add the green food coloring (a few drops) to the large bowl and beat for an additional minute.
Place the green frosting in a piping bag with a grass tip and pipe onto the cupcakes.
Add the orange food coloring (a few drops) to the reserved frosting and mix until combined. Place the orange frosting in a piping bag with a small round tip and pipe a beak, two dots for eyes, and feet onto the Reese’s Peanut Butter Eggs. Place the eyes on. Add the eggs to the top of each cupcake.