season the meat with salt and pepper then toss with flour to coat the meat evenly
heat some oil in a large pot at medium high, once sizzling add the beef and brown 3-5 minutes, then remove with a slotted spoon, leaving any juices, and set the meat aside
turn the heat to high, add the garlic and saute for about 30 seconds. Then add the Guinness.
Once the Guinness begins to simmer reduce heat to medium and scrape the brown bits off the bottom of the pan
Add the beef broth, HP, mustard and vegetables to the pot, stir to combine then bring to a boil, reduce to low and cover.
cook on low, covered for 55 minutes, stirring occasionally. Uncover and bring the pot to a light simmer and cook another 5-8 minutes until the liquid reduces a little and the broth thickens
If the stew is still too thin, you can either continue to simmer or stir together the corn starch and water, then add to the pot and stir to thicken.
serve with white rice