Make the jam:

1. Preheat the oven to 375F. Mix the strawberries, brown sugar, and balsamic vinegar together. Evenly distribute them onto a baking sheet—including any syrup that sits at the bottom of the bowl. Bake for about 30 min or until nicely caramelized.
2. Let them cool. Once safe to handle, throw everything into a blender and blend until desired consistency. (I like it a bit chunky, but thin enough to spread.) The jam can be stored in the fridge for about 3 days. So, I like to make it the day before I bake the cake.

Make the cake:

1. Grease your 8″ cake rounds and parchment the bottoms to make certain there is no sticking later. Preheat the oven to 350F.
2. Combine the flour, baking powder, baking soda, and salt in a large bowl and set aside.
3. In the bowl of a stand mixer, fitted with a paddle attachment, beat the butter until smooth. Add the sugar and continue to mix on medium speed until light and fluffy, about 5 min. Scrape down the bowl periodically to ensure everything is getting mixed.
4. With your mixer on low, slowly add the egg whites and vanilla. Turn the mixer up to medium for a moment once they have been added to ensure everything is incorporated. Scrape the bottom of the bowl to make sure there are no stray streaks of egg white.
5. With the mixer on low, alternate between adding your flour mixture and your buttermilk. Ideally, this is done in three batches, starting and ending with the flour mixture.
6. Once all ingredients are added, mix on medium speed for no more than 30 seconds, as over-mixing can make for a tougher cake.
7. Divide your mixture evenly between your prepared cake pans and bake for about 25 minutes. Check that your cakes are done by inserting a toothpick into the center—if it comes out clean, they’re ready. (Also if you don’t have toothpicks, gently press your finger into the center, if the cake springs back, they’re usually ready.
8. Let the cakes cool on a rack for about 10 minutes before running a knife around the edges and releasing the cakes from their pans. Let the cakes cool completely before frosting.

Make the frosting:

1. In the bowl of a stand mixer fitted with a paddle attachment beat cream cheese and butter until light and fluffy. Slowly add the powdered sugar 1C at a time, scraping down the bowl every so often to ensure everything is properly mixed.
2. If at 4 ½ C powdered sugar, you like the consistency no need to add more. If it is still too loose, add the last ½ C of powdered sugar. Beat for 3-5 min.
3. Add the peanut butter and beat until blended.
4. Switch to the whisk attachment and turn the mixer on medium-high. Very slowly begin streaming in the heavy cream. Once all the cream is added, whisk on high for 30 seconds.

Assemble!:

1. If your cakes have domed, slice off their tops so you have three even layers. Munch on scraps accordingly.
2. Spread the strawberry jam over one layer, then add a heap of frosting. Continue this pattern until you’re stacked. Cover the cake in frosting, then use a spoon to create the streaks of strawberry jam all around the cake.