Now spoon the Pastry Cream evenly over all the bottom layers set back in the pan. There is more pastry cream than you will need for this recipe: I end up using a little more than half. See Notes on what to do with the remaining.
Place each almond crusted top over the cream till all the tops are back where they belong on the cake. Now you can take the baking pan and set it in the fridge to help set the pastry cream.
When you are ready to assemble the cake, pull the pastry cream from the fridge to loosen up. Use a whisk to completely loosen it, removing as many lumps as possible, so that it will easily blend into the whipped cream (next step)
Leftovers can be stored in a sealed container (or even the baking pan sealed lightly with cling film and stored in the fridge for up to four days. If well wrapped, these squares can also be stored in the freezer!
To make sour milk, just add 1 tbsp of lemon juice or white vinegar to a cup of whole milk and let it sit for 15 minutes. Then it is ready to use if you don't have buttermilk or kefir on hand.
You can also use an 8 or 9 inch springform pan for baking the cake. Once cooled, you will slice it into wedges, and then follow the rest of the directions. You may find that the cake is thinner using a 9 inch springform pan, but it will still work.
This Pastry Cream recipe will give you more than you need for this cake, you may have just under half leftover, depending on how thick you layer it between the cake. Honestly, you could make less, but it makes for a great little dessert on its own, layered with fresh chopped fruit!