My favorite local bakery makes what they call Black Forest Cake which has a strawberry filling. It has two chocolate layers which are split in half to make four, whipped cream frosting and strawberry filling between the layers. The whole cake is coated with shaved chocolate. I love that cake, and I ask for it for my birthday each year.

You can make a nice strawberry filling by thickening frozen sweetened berries with cornstarch. These measurements are approximate. Thaw two 10-oz packages of frozen, sweetened, sliced strawberries. Strain them and put the juice in a heavy saucepan. There should be about 2/3 cup of juice. The measurement of cornstarch for that amount of juice would be 1 tablespoon. (If there is more juice, use a an appropriately larger amount of cornstarch; if there is less, add a bit of water or other fruit juice till it equals 2/3 cup.) Whisk the cornstarch into the cold juice; cook and stir over moderate heat until the juice bubbles and thickens; cook a minute or two longer. Stir in the drained berries and a tablespoon or two of a fruit liqueur, if desired. Orange-flavor is nice with strawberries, but the traditional kirsch would be nice too. Or just add a bit of lemon juice to brighten the flavor if you don't want to use liqueur.
Good luck with your cake!