You will need a pot that goes on the stove and in the oven, and a baking tray that drains (I like to use a cooling rack on a rimmed cookie sheet, but that roasting pan your oven came with could work too).
pre heat oven to 350F.
Lay bacon on a draining oven tray, and bake at 350F for 20 minutes.
Cut your sirloin steak into 2 cm cubes, cut your onions to match size, and parsnips to be sliced wider than your knife. Cut the lemon in half width-ways, then lay the flat side on the board with the little point up and cut in quarters.
cover cubes in salt and pepper and let them sit while your pot warms up.
heat pot on medium high heat, and warm up your ghee or oil (whatever you chose).
brown steak cubes in the hot fat on all sides a slight crust might form.
add corn starch to pot with cubes, a crust will definitely form.
add onions and parsnips let soften until they smell sweet,.
deglaze with beer.
add beef stock.
stir in the twigs of thyme, the bay leaves and the chunk of lemon.
this is when your bacon should be done, cut it into wide chunks about the same size as the beef and onions and add it to the pot. Don't turn off that oven, we'll need it soon.
bring to a simmer (you can use high heat if you want to, but a thick bottomed pot shouldn't need it).
Now that your stew is simmering put the whole pot in the oven and set it for 325F and bake for 3 or 4 hours.
Stir every hour, and watch as your stew thickens and becomes something magical.
Serving suggestions: I was going to make this into meat pies, so of course topping it with some puff pastry on a pie plate would be wonderful. If you are gluten free how about topped with mashed potatoes and baked off to make a cottage pie. My wife likes this on a bed of super crispy french fries and some room temperature cheese curds to make this the most English of all Poutines. A bed of rice and a side of peas works well with this too, but my favourite way is with roasted potatoes and sauteed mushrooms.