Season the lamb with salt and pepper.
Heat the oil in a large non-stick frying pan and fry the lamb for around 5 minutes over a medium heat until browned, turning regularly. You may need to brown the lamb in a couple of batches, depending on the size of your pan.
Transfer to the slow cooker, leaving the fat in the pan.
Return the pan to the heat and add the butter and onions, fry over a medium heat for 2-3 minutes until they begin to soften. Add the garlic, stirring constantly for around 30 seconds.
Add the flour and stir until all the flour is fully mixed in with the onions.
Gradually add the wine to deglaze the pan and then pour in the stock, tomato puree and stir together until all combined.
Pour the stock into the slow cooker with the lamb, add the bouquet garni, bay leaf, carrots, potatoes and season with some salt and pepper.
Cover with a lid and cook on high for around 6 hours. Half way through, add the peas and green beans and continue to cook until the vegetables are tender.
Divide the lamb stew into bowls or plates, sprinkle with some fresh parsley and serve with a warm buttered French baguette.
