- Preheat oven to 400°F. Line a large baking sheet with parchment paper.
- In a large bowl, toss mushrooms with one-half of oil and one-half each of salt and pepper. Spread mixture onto prepared baking sheet; bake until mushrooms are browning, about 30 minutes. Let cool.
- Meanwhile, in a medium skillet, heat remaining one-half of oil on medium. Add onion; cook until translucent, about 3 minutes. Stir in bell pepper, garlic and thyme; sauté until fragrant, about 3 minutes. Stir in spinach and remaining one-half of each salt and pepper. Transfer mixture to a large bowl; set aside.
- Transfer about one-quarter of roasted mushrooms to a cutting board and slice thinly. Place remaining mushrooms in a food processor. Pulse 6 to 8 times, until chopped but not puréed. Add rice, oats and flax; pulse 6 to 8 more times to incorporate (mixture should still have some chunks). Transfer to bowl with vegetable mixture; stir in eggs, cheese and mustard.
- Heat a cast-iron skillet on medium-high; mist with cooking spray. Pour in mushroom mixture and flatten top with a spatula. Bake 30 to 35 minutes, until firm and edges are golden.
- In the last 10 minutes of baking, prepare gravy: In a small saucepan, whisk together broth and arrowroot. Add sliced mushrooms, garlic and thyme. Bring to a boil then simmer, stirring, for 8 minutes. Remove garlic and thyme; whisk in butter.
- Slice bake into wedges; serve with mushroom gravy.
Related: The Power of Medicinal Mushrooms
- Serving Size 1/4 of recipe
- Calories 407
- Carbohydrate Content 33.5 g
- Cholesterol Content 179 mg
- Fat Content 24 g
- Fiber Content 6 g
- Protein Content 15 g
- Saturated Fat Content 10 g
- Sodium Content 599 mg
- Sugar Content 5 g
- Monounsaturated Fat Content 9 g
- Polyunsaturated Fat Content 3 g