Vegan White Lasagna with Mushrooms, Pesto, and Walnut Sausage

Ingredients

• 3 cups chopped mushrooms (We used a blend of shiitake and cremini.)
• 1/2 large onion (diced)
• 1 Tbsp olive oil
• 1/2 tsp sea salt
• 1/2 tsp black pepper
• 12 lasagna noodles
• 1 batch vegan pesto
• 1 batch sausage-style walnut meat
• 1 batch creamy roasted garlic sauce