6 tablespoons butter
1/4 cup all-purpose flour
1/4 cup chopped onion
1 bay leaf
1 whole clove
2 cups whole milk
2 (10 ounce) bags ready-to-use fresh spinach
Melt 4 tablespoons butter in heavy medium saucepan over medium heat.
Add flour and stir until light golden, about 7 minutes.
Stir in onion, bay leaf and clove.
Gradually whisk in milk.
Whisk until mixture boils and thickens, about 10 minutes.
Reduce heat to low and simmer 5 minutes longer, whisking frequently (sauce will be very thick).
Remove bay leaf and whole clove.
Cook spinach in large pot of boiling water just until wilted and tender, about 2 minutes.
Transfer spinach to bowl filled with ice water to cool.
Roll up spinach in kitchen towl and squeeze out as much liquid as possible.
Transfer spinach to processor and finely chop.
Add spinach to warm sauce, simmer over low heat until spinach is heated through, stirring often, about 5 minutes.
Stir in remaining 2 tablespoons of butter.
Season to taste with salt and pepper and serve.