Mushroom Wellington

January 9, 2023

Written by: Ava Elliott, Marketing Intern and Future Dietitian

Reviewed by: Devon Kroesché, MS, RDN, LDN

Happy New Year from us at Case Specific Nutrition to you! The holiday season can be very busy. If you are winding down from the rush of the holidays like me, and are interested in a warm meal, then this one is for you. My friend who has been making this vegetarian version of beef wellington for her family as a Christmas tradition shared this recipe with me. It contains vegetables like spinach and mushrooms that will both provide folate and spinach will provide some vitamin K. To make this recipe vegan, use a vegan puff pastry and swap the egg wash for a vegan egg wash.What You’ll Need:

  • 4 large portobello mushrooms
  • 3 large onions, chopped
  • 3 tbsp olive oil
  • 1 pkt spinach (10 oz)
  • 4 sprigs thyme
  • 1 puff pastry
  • 1 tbsp Dijon mustard
  • ½ tsp salt
  • ½ tsp pepper
  • Egg wash: 1 large egg and 1 tbsp 2% milk, beaten

What To Do:

  1. Sauté onions on medium-low heat with ½ tbsp olive oil, salt, and pepper. Stir occasionally and cook for about 15 minutes or until onions are golden brown. Remove onions.
  2. Sauté spinach and cook until wilted. Remove the pan from heat.
  3. Add 2 ½ tbsp olive oil to pan and cook mushrooms on medium-high heat until lightly browned, top side down. After about 5 minutes, turn mushrooms over and cook until golden brown. Drain on paper towel once removed from the heat.
  4. Cool onions, spinach, and mushrooms in the fridge completely.
  5. Preheat oven to 390° and prep baking sheet with Parchment paper.
  6. Add puff pastry sheet and spread half the caramelized onions in the center of puff pastry leaving 2/3 pastry on either side and ¾ in at the edge.
  7. Next, add half spinach over the onions and place mushrooms on top of spinach. Spread mustard over the mushrooms and sprinkle seasoning on top. Add the rest of the onions and spinach over the mushrooms.
  8. Delicately roll the pastry over the vegetable mixture into a log. Seal the edges and roll over so the seam of the pastry is facing down.
  9. Whisk together egg and milk and lightly coat pastry with egg wash. Place in the freezer for 10 minutes, followed by another layer of egg wash and free for another 10 minutes.
  10. Finally, bake for 30-35 minutes, until golden and pastry becomes flakey.

We hope you enjoy this recipe and share a picture with us on social media if you make it! Tag us at @casespecificnutrition on Instagram or Facebook. If you’d like to work with one of our dietitians, please email

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