In A Large Pot With Boiling Salted Water Cook Spaghetti Until Al Dente. Drain. In A Large Bowl Mix Together The Sour Cream, Grated Parmesan Cheese, And Minced Garlic. After Beating The Egg In A Small Bowl, Transfer To The Large Bowl And Blend Together. Transfer To A Greased Slow Cooker. Mix Cooked And Drained Spaghetti, 2 Cups Grated Monterey Jack Cheese, Thawed Spinach, And Half Of The French Fried Onions To The Slow Cooker. Stir Contents Of Slow Cooker Until Just Blended. Cover And Cook On Low For 6 To 8 Hours Or High Heat For 3 To 4 Hours. In Last 30 Minutes Of Cooking, Turn To High If Cooking On Low And Add Remainder Of Grated Monterey Jack Cheese And French Fried Onions To Top Of Casserole. Serve When Cheese Is Melted.