Preheat oven to 350°F (175°C) and grease two 4-inch cake pans with parchment paper liners.

In a medium bowl, whisk together flour, sugar, baking powder, and salt.

In a separate bowl, combine egg, milk, oil, and vanilla extract.

Gradually fold the wet ingredients into the dry ingredients until just combined.

Distribute the batter evenly into the prepared pans and bake for 18-20 minutes until a toothpick comes out clean.

Allow cakes to cool in pans for 5 minutes before transferring to a wire rack to cool completely.

Prepare buttercream by beating softened butter until smooth, then gradually adding powdered sugar and heavy cream until fluffy.

Divide the buttercream into separate bowls and tint with pastel food coloring.

Level the cooled cakes using a serrated knife and stack with a layer of buttercream in between.

Apply a thin crumb coat of frosting and chill for 15 minutes before applying the final layer of frosting.

Decorate the top with piped green frosting to simulate grass and place mini chocolate eggs in the center.