In a large saucepan, pour the water and bring it to a boil.
Add the frozen pearl onions, cover and boil for 5 minutes or until the onions are tender, then set aside. (Don't overcook the onions as they’ll be baked later on)
In another saucepan, melt the butter on medium to medium-low heat.
Stir in the flour, salt, and pepper until smooth consistency.
Gradually stir in the broth, milk, and whipping cream. Bring to a boil then cook and stir for 2 minutes or until thickened.
Stir in the parsley, cheese, and onions.
Remove from heat.
Pour into an ungreased 1-quart baking dish.
Cover and refrigerate overnight.
Remove from the refrigerator 30 minutes before baking.
Cover and bake at 350°F for 15 minutes.
Stir then bake uncovered for 10 more minutes or until bubbly.