Peel and halve the potatoes crosswise; transfer to a medium saucepan.
Cover the potatoes with hot water (from the tap) by about 1 inch; bring the water to a boil over high heat.
Peel the carrots, then trim off the ends; discard the peels and trimmings. Medium dice the carrots (cut into ½-inch cubes) and transfer to a medium bowl.
Trim off and discard the ends of the onion and remove the outer layer; small dice the onion (cut into ¼-inch pieces) and add to the bowl with the carrots.
1 medium yellow onion
Trim off and discard the root ends of the garlic; peel and mince or press the garlic. Add the garlic to the bowl with the other vegetables.
4 cloves garlic
Once the water in the saucepan is boiling, cook the potatoes until they are tender when pierced with a knife, 10 to 12 minutes.
Preheat a sauté pan over medium-high heat.
While the pan heats up, pat the beef dry with paper towels, then cut into 1-inch chunks; transfer to a medium bowl.
1 ½ lb striploin (New York strip) steak
Season the beef with salt and pepper; toss to coat.
1 tsp salt
½ tsp black pepper
Add the beef cubes to the pan in a single layer; cook, stirring occasionally, until the beef is browned but not fully cooked through, 4 to 5 minutes. Once done, transfer the beef to a bowl.
While the beef cooks, wash and dry the cutting board and knife.
Once the beef has been transferred, add butter to the pan, followed by the onions, carrots, and garlic. Cook, stirring occasionally, until the carrots begin to soften, 3 to 4 minutes.
2 tbsp butter, unsalted
Add Worcestershire sauce, salt, and pepper to the sauté pan; stir to combine.
2 tsp Worcestershire sauce
½ tsp salt
¼ tsp black pepper
Return the beef to the pan, then sprinkle the beef and vegetables with flour and stir to combine.
2 tbsp all-purpose flour
Add tomato paste and broth to the pan and stir to combine; increase the heat to high and bring the liquid to a simmer. Once simmering, reduce the heat to medium, cover the pan with a lid, and cook until the carrots are tender and the liquid is reduced, about 10 minutes.
2 tbsp tomato paste
16 fl oz (2 cups) chicken or vegetable broth
One by one, holding a sprig of thyme at its top, run you fingers down it to remove the leaves. Discard the sprigs and chop the leaves; stir about ¾ of the thyme into the stew and save the rest for garnishing.
Once the potatoes are tender, drain most of the water, but leave some for mashing. Add butter, salt, and pepper; mash with a potato masher until smooth.
2 tbsp butter, unsalted
½ tsp salt
¼ tsp black pepper
To serve, spoon the stew into a bowl, top with scoops of mashed potatoes, and garnish with the remaining thyme. Enjoy!