Pat osso buco dry with paper towel, brush with oil and sprinkle with salt and pepper. Heat a large cast iron pan with a lid over high heat and brown osso buco on both sides.
Add stock, onion, carrot, butter beans and bouquet garni. Bring to the boil, cover meat with a piece of baking paper and then the lid and place in oven for 1 ½ hrs or until beef is very tender.
Add the green beans for the last 10 minutes of cooking.
Place basil, pine nuts and garlic in a small food processor and process until finely chopped. Add olive oil and process until smooth. Stir through parmesan and season with pepper and salt if needed. Add lemon juice if desired.
Divide vegetables and sauce between 4 bowls and top each with a piece of osso buco and a dollop of pesto.
Bouquet garni is a small parcel of herbs, usually bay leaf, lemon peel, thyme, rosemary, but you can use whatever you have on hand.
If you're short on time, substitute basil pesto with a store-bought jar version.