Step 1

Preheat the oven to 375 degrees (176 degrees C). Butter a 10-inch spring form pan and fit the bottom with a round of parchment paper. Butter the parchment paper and then shake flour around in the pan to coat the inside of the pan completely. Shake out the excess flour and set aside.

Step 2

Add the flour, baking soda, baking powder, salt, cinnamon, cloves, and nutmeg to a large bowl and stir with a wire whisk to combine. (*See note)

Step 3

Peel and core the apples, and then chop them into chunky bite-size pieces, about the size you’d want if adding them to a fruit salad. Add the chopped apples to the flour mixture and stir to combine. Set aside.

Step 4

Separate the eggs so that you have 2 egg yolks in one bowl and 4 egg whites in a separate bowl. (Here's how to separate eggs.)

Step 5

Use an electric mixer to beat the butter, oil, and 3/4 cup (150 grams) of sugar on medium-high speed for 1 minute. Add the egg yolks, buttermilk, and vanilla and beat for 1 minute longer.

Step 6

Scrape the batter into the flour mixture and stir with a wooden spoon or spatula just until all the ingredients are combined and all the dry ingredients are moistened.

Step 7

Clean the mixing bowl and beaters of your electric mixer. Then use the electric mixer to beat the egg whites until they are foamy. (Or, use a handheld mixer.) With the mixer running, sprinkle in 2 tablespoons (25 grams) of granulated sugar. Continue beating until stiff peaks form (when you lift the beaters from the egg whites they form a peak that holds its shape). Using a rubber spatula or wooden spoon, gently fold the egg whites into the cake batter, stirring gently just until combined. Be careful to not over mix. It’s ok to have a few streaks of egg white in the batter.

Step 8

Scrape the batter into your prepared pan. Combine 2 tablespoons (25 grams) of sugar with 1/4 teaspoon of nutmeg and sprinkle the mixture evenly across the top of the cake batter.

Step 9

Bake the cake in the center of the oven for 50-60 minutes. To test for doneness, poke a toothpick into a few different places on the cake and inspect it for evidence of raw batter.

Step 10

Remove the cake from the oven and let cool completely on a wire rack before removing the sides of the pan.

Step 11

Pour the milk into a heavy-bottomed medium-size saucepan and cook over medium heat until bubbles appear along the edges of the pan.

Step 12

While the milk is heating, beat the sugar and egg yolks with an electric mixer until the mixture is thickened slightly and pale yellow, about 3 or 4 minutes. Beat in the cornstarch.

Step 13

With the mixer running, gradually pour the heated milk into the egg yolks in a thin steady stream. Stop the mixer halfway through pouring in the milk to quickly scrape down the sides of the bowl. Resume beating at medium speed to slowly add the remaining milk.

Step 14

Pour the mixture back into the saucepan and cook over medium heat, stirring constantly with a wooden spoon or spatula, until the sauce thickens enough to coat the spoon with a light, creamy layer. Do not let the mixture come close to boiling. The maximum temperature it reaches should be 170 degrees.

Step 15

Strain the sauce into a bowl through a fine mesh strainer and stir in the vanilla. Cover and refrigerate. Custard sauce can be served over Irish Apple Cake either warm or cold and will keep for 2 weeks, covered in the refrigerator.