Preheat oven to 350 degrees F.
Beat cake mix, strawberry gelatin, eggs, sugar, chopped fresh strawberries, milk, vegetable oil and all-purpose flour at low speed with an electric mixer for 1 minute. Scrape down sides, and beat at medium speed for 2 more minutes, stopping to scrape down sides, as needed. (The Strawberries should be well blended.)
Pour batter into 3 greased and floured 9-inch round cake pans.
Bake at 350 degrees for 23 minutes, or until cakes spring back when pressed lightly with a finger. Let cool in pans on wire racks for 10 minutes. Remove from pans, and cool completely (about 1 hour.)
Spread the Strawberry Buttercream Frosting between layers and on top and sides of cake. Garnish with whole and halved strawberries. Serve immediately, or chill for up to 1 week.
To make ahead: Prepare recipe as directed. Chill, uncovered, for 20 minutes or until frosting is set. Cover well with wax paper, and store in refrigerator up to a week. Strawberry Buttercream Frosting Ingredients • 1 Cup butter, softened • (32-ounce) Package powdered sugar, sifted • 1 Cup finely chopped fresh strawberries Preparation 1. Beat butter at medium speed with an electric mixer until fluffy (about 20 seconds). Add sugar and strawberries, beating at low speed until creamy. (Add more sugar if frosting is too thin, or add strawberries if too thick.)