How to Make It
Melt butter in a large skillet over medium heat. Stir in oil, onions, and 1/4 teaspoon salt. Cook, stirring occasionally, 15 to 20 minutes or until onions are golden brown.
Meanwhile, prepare pasta according to package directions; drain, reserving 1/4 cup hot pasta water.
Stir sherry and currants into onions; stir in kale. Cook, covered, 5 minutes or until kale is just tender, stirring occasionally. Stir in remaining 1/2 teaspoon salt.
Toss pasta with kale mixture and reserved pasta water. Sprinkle with cheese; garnish, if desired. Serve immediately.