Bring a large pot filled ¾ full of water to a boil for the pasta. While waiting for the water to boil, cook the apples.

In a frying pan over medium heat, add the chopped walnuts and toast lightly for about 3 minutes. Remove and set aside. To the same pan, add the slices of prosciutto one at a time and allow to crisp for about 10-15 seconds a side. Remove and rough chop, then set aside.

Wipe out the pan, then return to medium heat and melt 1 tablespoon + 1 teaspoon (18g) butter until the bubbling has stopped. Once butter has melted, add diced apples and toss in the butter to coat. Cook for 2 minutes until just soften on the outside, then remove the apples from the pan and set aside.

Once the pot of water boils, add 1 tablespoon salt and the pasta. If making store-bought dry pasta, cook following the package directions until al dente. If making homemade cavatelli, cook the pasta for 6-7 minutes until they float and are al dente. Remove cavatelli using a slotted spoon to a colander and toss with 1 tablespoon olive oil to prevent sticking. Reserve 1 cup of pasta water in case the sauce needs to be thinned later.

Next, in a large pot over medium heat, add the remaining 2 tablespoon butter (28g) until it foams. Add the flour and stir frequently for a few minutes. The flour should not brown, but it should cook in the butter, forming a white roux. After a few minutes, whisk in the milk, nutmeg, salt, and pepper. Turn the heat to medium-high and whisk until the mixture is smooth. Once it lightly starts to boil, it will begin to thicken. At this point, turn the heat down to low and add the cheese, stirring constantly. Continue stirring until the cheese has completely melted.

Add the pasta and reserved apples to the pot and stir to combine. If necessary (the sauce is too thick), add a little of the reserved pasta water. Once combined, serve with the prosciutto and walnuts as garnish.