Bake your white cake in two round pans according to directions and allow to cool. You may want to stick your rounds in the freezer for an hour so it’s easier to frost.
For FROSTING: Beat butter until smooth in large bowl. Slowly add about 1/2 of the powdered sugar. Then add the strawberries and mix on low speed. Continue to add the rest of the powdered sugar until you get a smooth consistancy. If it looks too thick add more strawberries. If it’s too thin add more powdered sugar until you get the right consistency.
Once the cakes are cooled spread jam over the first layer. Then add a layer of frosting. You could add a layer of thin strawberries here too. Then carefully add your second layer of cake. Add more frosting to fill in the gaps. Then frost the entire cake.