Preheat oven to 350 ºF (180 ºC)
In a large pan or Dutch oven on medium-high heat, add the oil.
Add in the beef and stir to brown on all sides.
Remove the beef to a plate. You will probably have to do this in batches.
Add in the diced onion and fry until they are starting to brown.
Add in the celery and brown along with the onion.
Add in the sliced mushrooms. Cover and cook down 5 minutes.
Add in the carrots, potatoes, and green beans, beef stock.
Stir to release any of the caramelized flavour from the bottom of the pan.
Add back in the beef, cover and place in oven to cook for 1 hour.
Remove from the oven.
In a small bowl stir the cornstarch and water to make a thin slurry.
Stir this into the gravy to make a thick sauce.
Add in the Worcestershire sauce and lemon juice.
Return to the oven 1 hour.
Adjust salt and pepper to your taste.
Once the sauce has stopped simmering, stir in the cream.
Serve warm with your favourite accompaniment.