Asparagus and Bread Soup with Pancetta

Name: Asparagus and Bread Soup with Pancetta
Ingredients: 1/4 cup diced pancetta; 1/4 cup extra-virgin olive oil; 1/2 cup thinly sliced onions; 1/4 cup thinly sliced shallots; 3 cloves garlic, whole; Salt and freshly ground black pepper; 4 cups chicken stock, plus more if needed; 1 cup small pieces country bread; 2 teaspoons fresh tarragon leaves; 2 cups 1-inch-long chopped asparagus; 2 cups spinach, washed; 1 teaspoon lemon juice; Chives, chopped, for garnish; Creme fraiche or sour cream, for garnish