• Preheat the oven to 375°F and butter or coat with cooking spray, a 2.5 quart oven-proof casserole dish.

For the Pasta:

• Fill a large saucepan with water and bring to a boil. Add the pasta and cook according to package instructions, only until the pasta is almost tender 8-10 minutes. The pasta will continue to cook in the oven while absorbing sauce. Drain the pasta, cover the saucepan and reserve.

For the Sauce:

• Add the leeks and wine to a large skillet set over medium-high heat, cover with a lid and wilt the leeks for 2 or 3 minutes allowing the alcohol in the wine to burn off and the leeks are just softened but still have a bright color. Transfer to a large mixing bowl and reserve while preparing the sauce.
• Using the same skillet set over medium-high heat, add the evaporated milk and bring just to a boil then reduce the heat to low.
• In a separate mixing bowl, add the grated cheddar, Parmesan cheese and the flour. Toss to fully combine. Add this cheese-flour mixture to the hot milk and cook over low heat, whisking to blend. In a small dish, add the mascarpone and one-half cup of the cheese sauce and blend to a smooth consistency. If needed, add additional sauce until the mascarpone is smooth, then whisk the mixture into the cheese sauce. Stir in the rosemary, salt and pepper. Remove from the heat.

To assemble:

• Combine the pasta, leeks and the cheese sauce in a large bowl, gently mix until well combined. Transfer the mixture to the prepared casserole dish.
• In a small dish, combine the bread crumbs, 1/4 cup of Parmesan cheese and the smokey paprika. Sprinkle the mixture over the top of the casserole.
• Transfer the casserole to the middle rack of the oven and bake for 20-25 minutes until heated through and the sauce is bubbly at the edges. Remove from the oven serve immediately.