Chayote with Onions (Chayote con Cebollas)

2 chayote squash (1 1/2 to 2 pounds total)
2 medium white onions
2 tablespoons butter or margarine
1 tablespoon vegetable oil
1/2 teaspoon dried oregano
1/4 to 1/2 teaspoon salt
Pinch of pepper

Pare and seed chayotes; cut lengthwise into 1/2-inch thick slices.

Cut onions lengthwise into halves. Cut halves lengthwise into 1/4-inch thick slices; separate into slivers.

Heat butter and oil in skillet over medium heat until foam subsides. Add onions and oregano; saut? over medium-low heat until onions are golden, 8 to 10 minutes.

Add chayote to skillet; saut? over medium heat, 3 minutes.

Cover skillet; reduce heat to low. Cook until chayote is crisp-tender, 8 to 10 minutes.

Season with salt and pepper.

Make 4 to 6 servings.