6 tablespoons (3 ounces or 85 grams) salted butter in 1T slices
1/2 cup plus 2 tablespoons 135 grams heavy cream cold is fine
to taste none Sea salt flakes for assembly
1 cup plus 2 tablespoons 225 grams granulated sugar
1/3 cup (45 grams) cornstarch
1/4 + 1/8 teaspoon sea salt fine
3 large eggs cold is fine
1 1/2 cups (355 ml) milk cold is fine
1 tablespoon vanilla bean paste or the seeds from 1 large vanilla bean
1 tablespoon (15 ml) vanilla extract
1 1/4 pounds 20 ounces (2 1/2 cups or 570 grams) unsalted butter firm-soft, not mushy
Equipment
Oven
9-inch cake pans
Stand mixer with paddle and whisk attachments
Skillet
Saucepan
Whisk
Plastic wrap
Cooling rack
Offset spatula
Piping bag
Directions
Melt butter in a skillet over medium heat. Add powdered milk and cook until browned. Let cool to lukewarm.
In a stand mixer bowl, combine sugar, flour, salt, baking powder, and baking soda. Mix on low for 30 seconds.
Add browned butter and mix on low-medium speed for 2 minutes. Scrape bowl and paddle. Mix on medium for 1 minute.
Heat oven to 325°F. Coat 3 9-inch cake pans with nonstick spray and line the bottoms with parchment paper.
With mixer running, add buttermilk. Scrape bowl and add eggs and vanilla. Mix until combined.
Divide batter between three pans. Bake for 17-20 minutes. Cool in pans for 5 minutes, then transfer to a rack to cool completely.
To make caramel filling, cook sugar in a skillet over medium-high heat until liquefied. Whisk until no lumps remain. Cook to deep amber color.
Add butter one tablespoon at a time, whisking to melt each piece. Slowly add cream, whisking constantly. Cook until caramel reaches 245°F. Let cool.
For frosting, in a saucepan, whisk together sugar, cornstarch, and salt. Add eggs one at a time, whisking in between. Add milk and vanilla bean paste.
Cook over medium heat, whisking constantly until thick. Remove from heat, whisk in vanilla extract. Let cool with plastic wrap on surface.
In a stand mixer, beat cooled custard for 2-3 minutes. Gradually add softened butter, beating between additions. Whip for 3-4 more minutes until fluffy.
For assembly, trim cakes for even layers. Coat each layer's top with frosting. Pipe a ring of frosting around the edges and freeze briefly.
Spread caramel on top of each cake layer, sprinkle with sea salt. Stack layers, spreading frosting and caramel as you go.
Apply a crumb coat of frosting to the cake. Chill until firm. Apply final layer of frosting, smoothing the sides with an offset spatula.