Prep the oven and pan: Preheat oven to 350°F (175°C). Line a 12-cup muffin tray with paper liners.
Mix the batter: Prepare the vanilla cake mix according to the box directions using eggs, oil, and water (or use your favorite homemade vanilla cupcake batter). Mix just until smooth.
Bake: Divide batter evenly among liners (about 2/3 full). Bake 18–22 minutes, or until a toothpick comes out clean.
Cool completely: Let cupcakes cool in the pan for 5 minutes, then transfer to a cooling rack until fully cool.
Make the buttercream: Beat softened butter until smooth and creamy (about 2 minutes). Add powdered sugar gradually, mixing on low so it doesn’t puff everywhere.
Adjust texture: Mix in milk and beat again until fluffy. If it’s too thick to pipe, add a tiny splash more milk; if too soft, add a little more powdered sugar.
Color the frosting: Tint most of the frosting yellow. Tint a smaller portion green for leaves and accents.
Pipe the florals: Fill piping bags. Use a star tip for swirls and small flowers. Add little blossoms and leaf accents with the green frosting.
Finish and serve: Arrange on a wooden board or serving tray and keep cool until ready to serve.