In a saucepan over medium heat, stir together ¾ cups strawberries, sugar and water until the sugar is dissolved. Heat the mixture to boiling, stirring often. Reduce heat and add the vanilla.
In a small cup, combine the cornstarch and tablespoon of water. Mix well.
Pour this into the boiling strawberry mixture. Stir and boil over medium-low heat for 3-4 minutes or until the mixture has thickened a bit.
Remove the pan from the heat.
Add ½ tablespoon of butter and mix until the butter has completely melted.
Allow the mixture to cool for 15 minutes, then add the last of the strawberries and stir to mix. Refrigerate the filling until you assemble the cake.
REPEAT THE STEPS ABOVE WITH THE BLUEBERRIES TO MAKE BLUEBERRY FILLING.
MAKE THE CAKE:
Using a stand mixer, beat the egg whites with the whisk attachment until they are stiff and form peaks. This may take a minute or two. Pour the egg whites into another bowl and place them in the refrigerator until you’re ready to add them to the batter.
Using the same bowl that you used to beat the egg whites, place the softened butter in and cream the butter for about 2 minutes (using the beater blade attachment until it is white in appearance.
Add the sugar to the butter and beat until fluffy (about another 1-2 minutes).
In a small bowl, combine the flour (measured carefully*), salt and baking powder. Set aside.
In another bowl, combine the milk and almond extract.
Add the flour mixture to the butter/sugar mixture alternately with the milk.
Add the stiffly beaten eggs to the cake batter. Fold the egg whites in gently. Do not overmix at this point. If you do, your cake will become more dense.
Grease and flour 3 8″ round cake pans. Pour the cake batter equally into the prepared cake pans.
Bake the cakes at 350 degrees for 20 minutes or until the top bounces back when you touch it.
Allow the cakes to cool for 10 minutes, then loosen the edges and remove them from the pans to a wire rack, allowing them to cool completely.
MAKE THE WHIPPED CREAM FROSTING:
Chill the metal bowl of a stand mixer (or a large metal bowl to use with a hand mixer for at least 5 minutes.
Add the heavy cream and powdered sugar to the bowl. Beat on high for 3-5 minutes or until stiff peaks form.
Place the frosting in the refrigerator until you are ready to assemble the cake.
ASSEMBLE THE CAKE:
Place a cake layer down on a cake plate. Spread a thin layer of whipped cream over it.
Use a slotted spoon to spoon one of the fruits on the cake. You may end up with some leftover and that’s ok (it’s amazing on ice cream!). Allow some of the liquid to drip off the spoon before gently placing it on the cake.
Place a second cake layer on top. Spread a thin layer of whipped cream on the second cake.
Then add the other fruit layer in the same way that you did the first.
Place the third cake layer on top. Frost the entire outside of the cake with the whipped frosting.
Garnish with fresh blueberries and strawberries as you’d like.
Serve this cake the same day as you make it. Store in the refrigerator until serving.