Put a large pot of water on to boil. Preheat oven to 450 degrees F. Coat an 8-inch-square (2-quart) baking dish with cooking spray.
Mix breadcrumbs, oil and paprika in a small bowl. Place spinach in a fine-mesh strainer and press out excess moisture.
Heat 1 1/2 cups milk in a large heavy saucepan over medium-high heat until steaming. Whisk remaining 1/4 cup milk and flour in a small bowl until smooth; add to the hot milk and cook, whisking constantly, until the sauce simmers and thickens, 2 to 3 minutes. Remove from heat and stir in Cheddar until melted. Stir in cottage cheese, nutmeg, salt and pepper.
Cook pasta for 4 minutes, or until not quite tender. (It will continue to cook during baking.) Drain and add to the cheese sauce; mix well. Spread half the pasta mixture in the prepared baking dish. Spoon the spinach on top. Top with the remaining pasta; sprinkle with the breadcrumb mixture.
Bake the casserole until bubbly and golden, 25 to 30 minutes.
Make Ahead Tip: Prepare through Step 4. Cover and refrigerate for up to 2 days or freeze for up to 3 months. Thaw in the refrigerator, if necessary, then bake for 35 to 45 minutes.
Tip: To make fresh breadcrumbs, trim crusts from whole-wheat bread. Tear bread into pieces and process in a food processor until coarse crumbs form. One slice of bread makes about 1/2 cup fresh crumbs. For dry breadcrumbs, spread the fresh crumbs on a baking sheet and bake at 250degreesF until crispy, about 15 minutes. One slice of fresh bread makes about 1/3 cup dry crumbs. Or use prepared coarse dry breadcrumbs. We like Ian's brand labeled "Panko breadcrumbs." Find them in the natural-foods section of large supermarkets.
Per serving: 576 calories; 22 g fat (11 g sat, 2 g mono); 69 mg cholesterol; 63 g carbohydrates; 37 g protein; 9 g fiber; 917 mg sodium; 403 mg potassium.