Pre-heat oven to 350 degrees. In the microwave, steam broccoli until tender, about 5 minutes. Set aside. In a small saucepot, heat milk until scalded. Add bouillon, stirring to dissolve. In a large sauté pan with butter, sauté onion until very soft and slightly golden brown. Add seasoned milk to onions and stir to combine. Add nutmeg, sugar, salt and pepper, mixing well. Cook until thickened. Remove from heat. In a bowl, whisk eggs. Temper by adding a small amount of cream sauce to eggs and whisking to combine. Add eggs into cream sauce and whisk. Fold in cooked broccoli florets. Mix gently until combined. Pour mixture into a casserole dish. Place dish into a large baking dish with 1-2 inches of water. Bake at 350 degrees for about 30 minutes or until knife comes up clean. The egg/milk mixture should be well set like custard. Serve immediately.