Combine heavy cream, stock, salt, and pepper in a medium-large pot on the stove. Bring to a boil. (Watch closely because you don't want the cream to burn.)
2 cups heavy cream, 2 cups vegetable stock, 1½ tsp kosher salt, ¼ tsp black pepper
Whisk in grits.
1 cup grits
Reduce heat to low. Grits should reduce to a light simmer.
Continue cooking, whisking often, until grits thicken. This will take anywhere from 20-60 minutes depending on the type of grits and size of the pot
Remove grits from heat. Whisk in butter and cheddar cheese.
2 tbsp butter, ½ cup shredded cheddar cheese
Notes
Note that the cooking time is longer for stone-ground vs quick grits. Quick grits will cook in 20-30 minutes, whereas stone-ground will be 40-60.