Step 1

In a large nonstick skillet, heat 1 teaspoon oil over medium heat. Add sausage and onion; cook and stir until sausage is lightly browned and onion is crisp-tender.

Step 2

Place spinach in a large bowl. In a small bowl, whisk vinegar, mustard and remaining oil. Drizzle over spinach; toss to coat. Add sausage mixture; serve immediately.