INGREDIENTS
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2 lbs. medium potatoes (red, Yukon gold, russet), peeled 2 Tablespoons unsalted butter 1/2 cup chopped onion 3 Tablespoons all-purpose flour 2 cups milk (I used skim) 1 teaspoon dry mustard Pinch cayenne pepper 1/2 teaspoon salt 2 cups (8 oz.) Sargen