In a saucepan, combine the frozen berries with the sugar. Bring to a boil over medium heat, then reduce to a simmer. Simmer for about 5-10 minutes, until the fruit is very soft, and some of the liquid has evaporated.
Remove from the heat, and immediately stir in the fresh berries. Let cool and chill completely before serving with the cake.
You can make the sauce up to 2 days in advance, keeping it stored in an airtight container in the refrigerator until needed. This recipe makes a generous amount of compote. If you have any leftover, you can eat it with yogurt and granola, or spoon it over oatmeal.
Vanilla Cake
Preheat the oven to 350 F, and position a rack in the center of the oven. Lightly spray the bottom of an 8-inch round cake pan with non-stick baking spray, or line with a circle of parchment paper. You can also use a 9-inch pan, but your finished cake will be a little thinner, and will need 5-10 less minutes to bake.
In a bowl, sift together the flour, sugar, baking powder and salt, then whisk until everything is evenly distributed.
In a separate bowl, whisk together the egg, egg white, buttermilk, melted butter, oil and vanilla.TIP: If you don't have buttermilk, juice a small lemon into a liquid measuring cup. You should get about 2 tbsp of lemon juice. Then add whole milk, up to the 3/4 cup line. Stir the lemon juice and milk together until thick and curdled, and add to the wet ingredients.
Add the dry ingredients to the wet, and whisk just until combined.
Pour the batter into the prepared pan, and bake for about 30-35 minutes, until the top springs back when lightly touched, and a cake tester or toothpick inserted in the center comes out clean.
Set the pan on a cooling rack, and cool completely before assembling with the cream and fruit sauce.
You can bake the cake up to 1 day in advance. When the cake is warm, turn it out of the pan, wrap it in plastic wrap, and keep it at room temperature until ready to assemble your cake.
You can make the cream 1 day in advance, keeping it refrigerated in an airtight container until needed. If you make this in advance, it may deflate slightly when you stir it up, so just re-whip it for a minute or two to thicken it again.
Assembly and Serving
You can serve the cake, cream and fruit sauce separately, or assemble it as shown in the photos. Keep in mind that once the sauce is spooned over the cream, the leftover cake does not keep well, so only do this if you plan on the whole cake being served and eaten in one sitting.
Pile the whipped cream on top of the cake and spread it out to the edges. Just before serving (and not a minute sooner), spoon some of the berry compote on top of the whipped cream, and serve the rest on the side.
Notes
Keep the cake, whipped cream and fruit compote separate, until ready to serve.
The cake can be wrapped in plastic wrap and kept at room temperature for up to 1 day, or frozen for up to 3-6 months.
The whipped cream can be refrigerated in an airtight container up to 1 day in advance.
The fruit compote can be refrigerated in an airtight container up to 2 days in advance.