Cooking : Asparagus and Water Chestnuts

Ingredients
2 teaspoons olive oil
1 teaspoon butter (optional)
1/4 cup diced red onion
1 (5 ounce) can sliced water chestnuts, drained
1 (10 ounce) package frozen cut asparagus
2 teaspoons balsamic vinegar

Directions
Heat the olive oil and butter in a skillet over medium-high heat. Add the onion, and saute for a few minutes to release the flavor into the oil. Add the water chestnuts, asparagus, and vinegar; cook and stir for about 10 minutes, until the asparagus is cooked but still crunchy.