Ingredients

1 tablespoon olive oil

1 small onion, chopped

4 small red potatoes (10 ounces), cut into 1/2-inch pieces

1 pound button mushrooms, trimmed and quartered

1/4 teaspoon dried thyme

Coarse salt

1 tablespoon tomato paste

10 ounces baby spinach leaves, rinsed well

1 can (14 1/2 ounces) navy beans, drained and rinsed

1 tablespoon red-wine vinegar, optional

Ground pepper

Preparation

In a large nonstick skillet, heat oil over medium heat; swirl to coat pan. Add onion and potatoes; cook until onion is lightly browned, 8 to 10 minutes. Add mushrooms, thyme, and salt; cook, stirring often, until mushrooms are tender, 8 to 10 minutes.

Stir in tomato paste and 2 cups water; cover, and cook until potatoes are tender, 8 to 10 minutes.

Add half the spinach; cover, and cook until wilted, about 1 minute. Add remaining spinach and beans; cook, covered, until heated through. Stir in vinegar, if desired. Season with salt and pepper, and toss to combine.