Peel the potatoes and cut them into roughly 1-inch chunks. This helps them cook evenly and mash easily later.
Chop the onion into fine pieces and mince the garlic; these will melt into the soup, adding sweetness and aroma.
Add the chopped potatoes, onion, and garlic to the crockpot, then pour in the broth until all ingredients are just covered.
Set the crockpot to low and cook for 6 to 8 hours, until the potatoes are fork-tender and start to break down, filling the house with a warm, earthy aroma.
Use a potato masher or an immersion blender to mash the potatoes directly in the crockpot, creating a smooth or chunky base depending on your preference.
Stir in the heavy cream and shredded cheddar cheese until the cheese melts completely, making the soup rich and velvety. Taste and season with salt and pepper as needed.
Let the soup sit for about 5 minutes to thicken slightly and allow flavors to meld. Give it a final stir, then ladle into bowls to serve hot, garnished with extra cheese or herbs if desired.