Gratineed Mustard Creamed Onions

Ingredients

• 3 tablespoons cream sherry 
• 1 tablespoon dijon mustard 
• 2 tablespoons flour all-purpose
• 1 tablespoon grainy mustard 
• 0.3 teaspoon nutmeg grated
• 0.5 cup parmigiano-reggiano grated
• 2 pound pearl onions white
• 2 tablespoons butter unsalted
• 1 cup milk whole

Equipment

• oven
• whisk
• pot
• baking pan
• broiler

Directions

1. Cook onions in a large heavy pot of boiling salted water (2 teaspoons salt for 4 quarts water) until just tender, 25 to 30 minutes. Reserve 1 cup cooking water, then drain (reserve pot). Cool onions to warm, then peel.
2. Melt butter in dry pot over medium heat.
3. Add flour and cook, stirring, 2 minutes.
4. Whisk in reserved cooking water, milk, and Sherry and cook, whisking frequently, until mixture is thickened, about 8 minutes.
5. Whisk in mustards, nutmeg, and 1/2 teaspoon each of salt and pepper.
6. Add onions to sauce and simmer 5 minutes.
7. Preheat broiler.
8. Transfer creamed onions to baking dish and sprinkle evenly with cheese. Broil 4 to 5 inches from heat until top is golden brown and bubbling, about 3 minutes.
9. Creamed onions, without cheese, can be made (but not gratinéed) 1 day ahead. Chill, uncovered, until cool, then covered. Bring to room temperature, then reheat in a 400°F oven about 20 minutes before sprinkling with cheese and broiling.