Heat oven to 350'F. Combine first 5 ingredients. Brush 1 phyllo sheet with butter. (Keep remaining phyllo covered with a damp towel to prevent drying.) Fold sheet in half crosswise; brush with butter. Fold in half crosswise again; brush with butter. Place 1/3 cup SPAM mixture in center of sheet. Fold long sides up and over filling, overlapping slightly. Fold into thirds from narrow edge. Place seam side down on baking sheet. (Cover with damp towel to prevent drying.) Repeat with remaining phyllo sheets. Bake 20 minutes or until golden. Serve with Mustard Sauce. MUSTARD SAUCE: In saucepan, combine all ingredients. Heat over low heat, stirring occasionally, until warm.