Make This Rack Of Lamb With Citrus Gremolata

Ingredients

• About 1 pound lamb bones
• 1 small white or brown onion
• 1 stick celery and a few leaves
• 1 bay leaf
• 1 sprig rosemary
• A few peppercorns
• 2 tablespoons extra-virgin olive oil
• Scant 1/2 cup white wine
• 12 1/2 cups cold water
• 2 teaspoons corn flour
• 1/2 tablespoon butter
• salt
• 2 French-trimmed 8-bone racks of lamb
• Salt and freshly ground black pepper
• Small handful mint leaves
• 2 strips orange zest
• 2 strips lemon zest
• 4 teaspoons Dijon mustard
• 7 ounces Swiss chard leaves
• 5 tablespoons extra-virgin olive oil
• 1 clove garlic