Place a large pot of water on to boil and once boiling, add two teaspoons kosher salt then the shells. Cook for 9 minutes then remove and rinse with cold water and set aside.

Preheat oven to 425 degrees F.

In a large sauté pan, melt butter in oil and add onions and prosciutto and cook for three minutes over medium high.

Add ground chicken meat, sage and garlic and cook just until the chicken is just undercooked. A few undercooked pink pieces is fine since it will continue to cook in the oven.

Cool this mixture a little to about room temperature.

In a large bowl, mix eggs, both bread crumbs, cheese, parsley, pepper and basil.

Add the cooked mixture to the bowl and stir to combine.

Divide the mixture between the 20 shells and place on your counter or cutting board while you make the sauce

Heat a medium sauce pan over medium heat and add butter to melt.

Once melted, add flour, stir and cook for three minutes.

Add milk and whisk to form a thick sauce.

Whisk in the half and half to finish the sauce along with the salt, pepper, mustard and nutmeg.

Cook over medium for a few minutes then remove from heat.

In a 9×13-inch pan, ladle a little of the sauce on the bottom and place the 20 stuffed shells onto the sauce, stuffing side up.

Lade the remaining sauce over the top of each shell and cover with parchment and foil.

Bake for 25 minutes covered and 5 minutes uncovered.