Prepare Mushrooms: Clean and slice the mushrooms. If using wild mushrooms, rinse under cold water. For button mushrooms, wipe with a damp cloth.
Sauté Onions & Garlic: In a large skillet, heat vegan butter or olive oil over medium heat. Add the onion and cook until soft and translucent (about 7-10 minutes). Add garlic and cook for another 30 seconds.
Cook Mushrooms: Add mushrooms to the pan and sauté for 7-10 minutes until browned and liquid evaporates.
Make Sauce: In a small bowl, whisk vegetable broth, Dijon mustard, smoked paprika, salt, and pepper. Stir in arrowroot/cornstarch slurry (mix with water) to thicken.
Combine: Pour sauce mixture over the mushrooms, simmer for 3-5 minutes, then add coconut milk. Simmer for another 2-3 minutes. Taste and adjust seasoning as needed.
Serve: Serve with mashed potatoes, rice, or pasta. Garnish with fresh parsley.