Portobello and Roast Beef Sandwiches with Balsamic Onions

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Portobello and Roast Beef Sandwiches with Balsamic onions

Dominic Perry

This hearty roast beef sandwich is topped with creamy balsamic onions and crisp fresh spinach. It’s delicious when the portobello mushrooms are still hot from the oven, but it’s also great cold, so feel free to make it tonight for tomorrow’s lunch.

Prep and cook time: 20 min. Servings: 4 (1 sandwich)

Gluten Free


  • 8 med. portobello mushroom caps (each cap about 3-in. wide)
  • cooking spray
  • 1 med. yellow onion, sliced
  • 2 T. balsamic vinegar
  • ½ t. brown sugar
  • ¼ c. water
  • pinch salt
  • 1 T. fat-free Greek yogurt
  • 8 oz. lower-sodium roast beef
  • 2 c. baby spinach leaves


  1. Preheat the broiler to high.
  2. Remove the stems from the mushroom caps and set aside. Spray mushroom caps with cooking spray and broil until tender, about 4 min. on each side.
  3. While the mushrooms are cooking, make the balsamic onions. Cut the onion and reserved mushroom stems into thin slices. Spray a medium skillet with cooking spray and add the onions, mushrooms, balsamic vinegar, brown sugar and water. Cook over medium heat until the vinegar and water have boiled off and the onions and mushroom pieces are tender. Remove from heat and stir in salt and yogurt.
  4. Build the sandwiches: Divide the roast beef among four mushroom caps. Top each with spinach leaves, the onion mixture and another mushroom cap. Secure with a skewer if desired.

Nutrition Information

Per serving: 160 calories (25 from fat), 3 g total fat (1 g saturated fat), 35 mg cholesterol, 138 mg sodium, 14 g carbohydrates, 3 g fiber, 7 g sugar, 21 g protein. Exchanges: ½ starch, 1 vegetable, 3 protein, 1 fat.

GLUTEN-FREE recipes are prepared without any wheat, barley, rye or triticale. Check the label on each ingredient to make sure the brand you are using does not contain these grains in any form (flour, bread, stuffing, bran germ, malt, starch, etc.).

All exchange values are approximate. When an optional or additional ingredient is offered, exchange values may change.

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