Preheat oven to 400°F.
Using 1 pound bacon, tightly weave strips into square shape roughly size of pie dish, alternating strips over and under. Gently place in pie dish and press down firmly.
On baking sheet, weave remaining 3/4 pound bacon into second square shape to serve as lattice top for pie. Place pie dish and baking sheet in oven and bake 15 minutes. (Bacon will not be fully crisp at this point, but will finish cooking in second baking step.) Remove from oven allow to cool slightly. Use paper towel to absorb excess grease.
While bacon cooks, cook pasta according to package directions, drain and set aside.
In saucepan, melt 4 tablespoons butter over medium heat. Stir in flour, whisking to combine. Add milk slowly while stirring constantly. Reduce heat to low and stir in cheeses. Cook 1-2 minutes until cheese is melted. Pour pasta mixture into pie dish over bottom bacon crust.
Melt remaining 2 tablespoons butter in skillet over medium heat. Add breadcrumbs and brown. Top pasta mixture with breadcrumbs and sprinkle with nutmeg and basil leaves.
Cover pie with bacon lattice top and bake at 400°F for 15 minutes. Cool slightly before serving.