In a large pot, add the potatoes and fill with salted water until they’re covered. Bring to a low boil and cook until your potatoes are soft and can be easily pierced with a fork. Prepare the stew while the potatoes cook.
Drain the cooked potatoes and mash with a potato masher, ricer or hand held electric mixer. Stir in the butter and cream. Season with salt and pepper to taste, cover and set aside.
While the potatoes cook, make the stew. In a large frying pan on medium heat add the butter and heat until melted. Add the diced onion and cook until soft and translucent, 4-5 minutes. Add the crushed garlic to the pan and cook until fragrant, about 1 minute. Add the mushrooms to the pan and cook 5-7 minutes until they begin to soften. Add the carrots and continue to cook for another 5-7 minutes, stirring occasionally.
While the stew simmers heat the mashed potatoes if needed (heat in the microwave, on the stove, or in the oven adding additional butter or milk as needed to loosen). Serve the stew over the mashed potatoes and enjoy!