Grilled Mushroom Burgers with Tarragon Crema - Forks Over Knives

Ingredients

• ⅓ cup raw cashews, soaked in very hot water for 15 minutes
• 1 tablespoon tahini
• 1 tablespoon Dijon mustard
• 1 tablespoon lemon juice
• 1 small clove garlic, minced
• ¼ to ⅓ cup unsweetened, unflavored plant-based milk
• ¼ cup fresh tarragon, chopped
• Freshly ground black pepper, to taste
• 4 portobello mushrooms, stems removed
• 1 tablespoon balsamic vinegar
• 4 whole grain hamburger buns, split and toasted
• 1 cup fresh spinach
• 4 slices tomato