Best Birthday Cake

Preheat oven to 350°F. Butter two 9-inch round cake pans and line with circles of parchment paper, then butter parchment.

Sift together flour, baking powder, baking soda, and salt in a medium bowl.

In a large mixing bowl, beat butter and sugar with an electric mixer at medium speed until pale and fluffy, then beat in vanilla.

Add eggs one at a time, beating well and scraping down the bowl after each addition.

At low speed, beat in buttermilk until just combined (mixture will look curdled).

Add flour mixture in three batches, mixing until each addition is just incorporated.

Spread batter evenly in cake pan, then rap pan on counter several times to eliminate air bubbles.

Bake until golden and a wooden pick inserted in center of cake comes out clean, 35 to 40 minutes.

Cool in pan on a rack 10 minutes, then run a knife around edge of pan. Invert onto rack and discard parchment, then cool completely, about 1 hour.

For frosting: Combine the chocolate and espresso powder in the top of a double-boiler or in a heatproof bowl over simmering water. Stir until the chocolate is melted.

Remove from heat and let chocolate cool until tepid.

Whisk together the sour cream, 1/4 cup of the corn syrup, and vanilla extract until combined.

Add the tepid chocolate slowly and stir quickly until the mixture is uniform.

Taste for sweetness, and if needed, add additional corn syrup in one tablespoon increments until the desired level of sweetness is achieved.

Let cool in the refrigerator until the frosting is a spreadable consistency. This should not take more than 30 minutes.

Should the frosting become too thick or stiff, just leave it out until it softens again.