Cake: 
Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large bowl, beat sugar, eggs, and vanilla until fluffy. Add milk and vegetable oil, mixing until combined.
In a separate bowl, whisk flour, cocoa powder, baking powder, baking soda, and salt. Gradually mix dry ingredients into the wet mixture.
Stir in boiling water until the batter is smooth and thin.
Divide the batter evenly between the pans and bake for 30-35 minutes, until a toothpick comes out clean. Cool completely in pans.
Strawberry Filling: Combine strawberries, sugar, lemon juice, cornstarch, and water in a saucepan over medium heat. Cook until thickened, about 5-10 minutes. Let cool.
Assembling the Cake: Once cakes are cooled, level them if needed. Spread the strawberry filling over the first cake layer, then place the second layer on top.
Frosting: Beat softened butter until creamy. Gradually add powdered sugar and cocoa powder. Mix in heavy cream and vanilla, beating until smooth. Frost the top and sides of the cake. Garnish with extra strawberries if desired. 
Enjoy this irresistible treat! 
