Vegetarian loaf

Name: Vegetarian loaf
Ingredients: 1/2 cup brown rice, dry; 1 large yellow onion, chopped; 2 garlic cloves, minced; 2 celery ribs, chopped; Kosher salt; freshly ground black pepper; 10 ounces crimini mushrooms, stems removed, sliced thin; 1 tablespoon fresh tarragon, chopped; 6 ounces fresh spinach; 3 ounces sun dried tomatoes, chopped; 4 eggs, whisked; 1 tablespoon Dijon mustard; 2 tablespoons vegetable broth