Cut enough young squash into roughly 1” cubes to make four cups (about 4-6, depending on size) , boil until just tender, drain, and set aside. Make two cups of white sauce with whole milk and butter, add about a cup of sour cream, a half cup fresh-grated/shaved Parmesan, and a lightly beaten egg.
Stir in two cups cooked young limas, a quarter cup of minced white onion. Mix with squash, add salt and white pepper to taste, and stir gently. Top with more Parmesan, and bake at 350 until lightly browned and bubbling.
