1. Heat oven to 350 degrees . Bring a large pot of lightly salted water to a boil. Cook pasta 2 minutes less than package directions (about 13 minutes). Drain.
2. Meanwhile, combine 2 tbsp of the butter and the milk in a medium saucepan over medium heat. Bring just to a simmer and stir in Neufchatel. Toss cheddar with cornstarch and stir into saucepan along with salt and pepper until melted and smooth. Simmer 2 minutes, stirring frequently. Remove from heat and stir in peas and pasta.
3. Melt remaining 1 tbsp butter in a small skillet over medium-high heat. Add cracker crumbs and stir to mix. Brown 1 minute.
4. Coat 8 individual baking dishes with nonstick cooking spray. Divide macaroni mixture among prepared dishes. Top each with about 1 tbsp cracker crumbs. Bake at 350 degrees for 20 minutes.