Step 1

Place onions into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 10 minutes.

Step 2

Drain and use a slotted spoon to transfer to the onions to an ice bath.

Step 3

Melt butter in a large skillet over medium heat. Cook and stir flour into melted butter for about 5 minutes. Season with salt and pepper.

Step 4

Add cream to flour mixture. Cook and stir until bubbly and thick, about 5 minutes. Stir onions, parmesan, and parsley into cream sauce.

Step 5

Cook until heated through, about 2 to 3 minutes. Add onions to baking or serving dish.