Boil the potatoes: Preheat broiler to high or oven to 500 degrees. Peel and dice the potatoes into 1/2-inch cubes. Place the potatoes in a medium pot with a large pinch of salt and enough water to cover. Bring to a boil, then reduce to a simmer for 10-12 minutes, until fork tender.

Prep the ingredients: While the potatoes cook, thinly slice the mushrooms. Halve, peel, and dice the onion. Quarter the Brussels sprouts. Strip the thyme off the stems and roughly chop the leaves. Mince or grate the garlic.

Start the veggie ragout: Heat a drizzle of oil in a medium pan over medium-high heat. Add the mushrooms to the pan and cook, tossing, for 4-5 minutes, until golden brown. Season with salt and pepper and set aside. Drain the potatoes and return to the pot, if ready.

Heat another drizzle of oil in the same pan over medium heat. Add the onion to the pan and cook, tossing, for 3-4 minutes, until softened. Add the Brussels sprouts, thyme, and garlic to the pan and cook, tossing, for another 3-4 minutes, until the Brussels sprouts have softened slightly. Season with salt and pepper.

Make the veloute: Stir 1 tablespoon butter into the pan to melt, then sprinkle the flour over the vegetables. Stir to combine. Very slowly stir 1 cup water and 1 stock concentrate into the pan, until thoroughly combined. Bring mixture to a simmer for 4-5 minutes, until reduced and very thick. Remove pan from heat. HINT: If you don’t have an oven-proof pan, transfer mixture to an 8x8-inch baking dish after this step.

Using a potato masher or fork, mash the potatoes in the pot over medium-low heat. Mash in the remaining stock concentrate, 1/3 cup water, and the cheddar cheese. Once completely smooth, taste and season with salt and pepper.

Evenly spread the cheddar mash over the vegetable ragout in the pan. Place the pan under the broiler for 3-4 minutes, until golden brown. Serve right out of the pan and enjoy!