In a large bowl, mix the first 4 ingredients (beef through thyme). Form beef mixture into 4 patties.
Brush mushroom caps with olive oil and season with sea salt and freshly ground black pepper to taste.
Place burgers and mushrooms on the grill. Close lid and cook burgers for 5 to 10 minutes on each side, until beef reaches preferred doneness. Cook mushrooms for 2 to 5 minutes on each side, until tender.
In a medium bowl, mix the avocado with the cilantro and sea salt and freshly ground black pepper to taste.
Layer, 1 mushroom cap, spinach, burger, onion, guacamole and second mushroom cap. Serve warm.
Notes
SERVING SUGGESTION: A Big Salad tossed with Leanne’s Basic Vinaigrette (In a large bowl, toss together torn lettuce (not Iceberg - no nutrition) and salad veggies of your choice. In a small bowl, whisk together 3 tablespoons extra virgin olive oil, 1 tablespoon balsamic vinegar, 1 clove pressed garlic and a pinch of dried basil and oregano; drizzle dressing over salad.)NUTRITION: 409 Calories; 32g Fat; 23g Protein; 9g Carbohydrate; 3g Dietary Fiber; 85mg Cholesterol; 103mg Sodium. Exchanges: 0 Grain (Starch); 3 Lean Meat; 1/2 Vegetable; 0 Fruit; 4 1/2 Fat.