1 lb. (or more) Pearl onions, white or mixed colors
2 Tb. Butter
2 Tb. Flour
1 1/2 c. Whole milk
1/2 tsp. Salt
1/4 tsp. White pepper (or black)
1-2 Tb. Worcestershire sauce
1-2 Tb. Dry cooking sherry (optional)
Put onions in a large saucepan and fill with water. Place pan on stove and heat to boiling. Reduce to simmer and cook 7 minutes (set a timer). Remove from heat and strain off water, reserving about 1/2 cup cooking water. Rinse onions with cold water and then peel and cut off ends. Set aside in a bowl.
In a medium saucepan over medium-low heat, combine butter and flour by whisking them until they are light brown and start to bubble. Gradually add all the milk, whisking constantly. Cook/whisk another 2-3 minutes, until thickened. Mix in the cooking water and add salt, pepper and Worcestershire sauce. Add the onions and let stand covered until serving.
These may be refrigerated for several hours and reheated slowly on the stove. Do not let the mixture boil. If too thick, add milk as necessary. Salt and pepper to taste and add cooking sherry if desired.