Preheat oven to 350 degrees F (175 degrees C). Grease four 9-inch round cake pans and line with parchment paper.
Combine sugar and butter in a stand mixer fitted with the paddle attachment; beat until smooth and creamy. Beat in eggs one at a time. Mix in 1 cup flour. Beat in 1/2 cup milk. Repeat with remaining flour and milk, beating briefly after each addition. Scrape down sides of bowl and mix in vanilla extract.
Pour batter evenly into the prepared cake pans. Smooth the tops with a spatula.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 15 minutes. Cool cakes in the pans for 10 minutes; invert onto a wire rack to cool completely, about 20 minutes.
Mix sour cream and sliced strawberries together in a large bowl. Spread evenly between the cooled cake layers.
Frost top and sides of cake with whipped topping. Decorate top of cake with whole strawberries and mint leaves.