Adjust an oven rack to the middle position. Preheat the oven to 350F [180C]. Butter and flour two 8 by 2 in [20 by 5 cm] round cake pans and line the bottoms with parchment paper.

In a medium bowl or liquid measuring cup, whisk the eggs, egg yolks, buttermilk, sour cream, oil, and vanilla.

In the bowl of a stand mixer fitted with a paddle, mix the flour, sugar, almond flour, baking powder, salt, and baking soda on low until combined. With the mixer running on low, add the butter one piece at a time, beating until the mixture resembles coarse sand. With the mixer still running on low, slowly add half the wet ingredients. Increase the speed to medium and beat until incorporated, about 30 seconds. With the mixer running on low, add the rest of the wet ingredients, mixing until just combined. Increase the speed to medium and beat for 20 seconds (the batter may still look a little bumpy). Scrape down the sides and bottom of the bowl and use a spatula to mix the batter a few more times.

Divide the batter between the prepared pans and smooth the tops. Tap the pans gently on the counter 2 times each to help get rid of any bubbles. Bake 28 to 36 minutes, rotating the pans halfway through, until the cakes are golden brown and pull slightly away from the sides and a wooden skewer or toothpick inserted in the centers comes out clean (or an instant read thermometer reads 210 to 212F).

Transfer the pans to a wire rack and let cool for 3 or 4 minutes. Run a knife gently around the edge of the cake to help release it from the sides, then let the cakes continue cooling in the pans until just warm, about 15 minutes. Run a knife gently around the sides again, and then turn the cakes out onto the rack, remove the parchment paper, and let cool completely. Once cool, the cakes can be frosted, or be wrapped in plastic and refrigerated overnight.

Pour 1 in [5 cm] of water into a medium saucepan over medium heat and bring it to a gentle boil.

Melt the chocolate in a heatproof bowl set over the pan of boiling water, being careful not to let the water touch the bottom of the bowl. Stir constantly until just melted and set aside to cool slightly.

In the bowl of a stand mixer fitted with a paddle, beat the butter and salt on medium speed until light yellow and fluffy, about 3 minutes. Add the vanilla and corn syrup and beat on medium speed until combined. Lower the speed to low and gradually add the confectioners’ sugar. Beat on medium speed, stopping to scrape down the sides of the bowl as necessary, until smooth and creamy, 2 to 3 minutes. Add the chocolate and mix on low speed until no streaks remain. Use a rubber spatula to mix the frosting a few more times, making sure it is completely combined.

Notes: the almond flour causes the cake to stick a little more than usual to the sides. Make sure to grease the pans very well and use a parchment liner on the bottom. This cake can also be baked in three pans, but please note you will have to take some time off the final baking time.