Spring Minestrone with Caramelized Garlic Broth

Name: Spring Minestrone with Caramelized Garlic Broth
Ingredients: 1 head garlic; 1 medium yellow onion; 1 medium fennel bulb with fronds; 2 medium or 4 small leeks; 6 tablespoons extra-virgin olive oil, divided; 1 bay leaf; 8 cups water; 2 3/4 teaspoons kosher salt, divided; 1 medium lemon; 1 (15-ounce) can white beans, such as cannellini or Great Northern; 1 cup fresh or frozen green peas; Freshly ground black pepper; Large handful pea shoots, for serving (optional); Freshly grated Pecorino Romano cheese, for serving (optional)