Cut potatoes into bite-sized pieces and add to the crockpot. If using russet potatoes, peel them first.
In a medium nonstick pan or cast iron skillet, heat oil and butter over medium-high heat until butter is melted and bubbly.
While butter melts, toss stew meat in 2 tablespoons of flour to coat, and season with salt and pepper. Reserve the remaining 2 tablespoons of flour for the dumplings.
Add the beef to the pan in 2–3 batches, making sure not to overcrowd the pan. Brown for 2–3 minutes per side, until nicely browned. You want to develop some color, but not cook the meat through.
As each batch of beef is browned, transfer it to the crockpot with the potatoes. Repeat with the remaining beef, adding a little more oil to the pan if needed.
Add the carrots, celery, mushrooms, onions, and garlic to the pan you browned the meat in, season with salt and pepper, and toss to combine.
Cook 2–3 minutes over medium heat to get a bit of color on the veggies, and transfer to the crockpot.
Add the beef stock, wine, Worcestershire sauce, Kitchen Bouquet, rosemary, and bay leaves.
Cover crockpot with lid and cook on low for 6–8 hours, or on high for 4–5 hours, until meat is tender and breaks easily with a spoon and potatoes are cooked through. Remove bay leaves and rosemary before adding the dumplings.
To make the dumplings, cut each biscuit into 4 equal pieces, then gently roll each piece into a ball. Lightly coat the dough balls in the reserved 2 tablespoons of flour. This helps the dumplings hold their shape and thickens the gravy as they cook.
Arrange the dumplings over the top of the stew, cover, and cook on HIGH for 40–45 minutes, without stirring, until the dumplings are puffed up and fluffy. To check for doneness, cut one dumpling in half. The center should be fully cooked, with no wet or raw dough remaining.