Traditional Mexican Caldo de Res (Beef Soup) with Tender Shank

Ingredients

• 2 lb (900 g) bone-in beef shank, cut into large pieces
• 1 lb (450 g) beef marrow bones or beef soup bones
• 10 cups (2.4 L) water, plus more as needed
• 1/2 medium white onion
• 4 garlic cloves, lightly crushed
• 2 bay leaves
• 4 cilantro stems
• 2 sprigs fresh mint, optional
• 2 teaspoons kosher salt, plus more to taste
• 2 ears corn, each cut into 3 pieces
• 3 medium carrots, peeled and cut into thick pieces
• 1 large chayote, peeled, pitted, and cut into chunks
• 2 medium potatoes, peeled and quartered
• 6 oz (170 g) green beans, trimmed and halved
• 2 Mexican squash or zucchini, cut into thick half-moons
• 1/3 head green cabbage, cut into wide wedges
• 1 cup (165 g) cooked garbanzo beans, optional
• 2 Roma tomatoes, chopped
• 1 small garlic clove
• 2 tablespoons chopped white onion
• 1/4 cup (60 ml) broth or water
• 1/2 cup chopped fresh cilantro
• 2 limes, cut into wedges
• 1 serrano pepper, thinly sliced, optional
• Warm corn tortillas