1) Combine cream, shallot, garlic, salt, pepper, thyme, and red pepper flakes in a small pot and heat over low heat until it’s steaming. Let it simmer for about 10 minutes, stirring regularly. Then pulse mixture in a food processor or just mash it together to mash up shallot and garlic.
2) Wash potatoes well and either A) slice potatoes thin with a mandolin or just cube into 1/2-inch cubes. Divide potatoes between four foil packets. Double wrap the foil on the bottom to make sure it doesn’t tear.
3) Once potatoes are in foil packets, pour cream mixture over the potatoes. Divide it evenly. Cover packets with more foil and seal tightly.
4) Cover grill and grill the packets over low indirect heat (if you’re using a gas grill turn off all the burners except one and cook the foil packets off the burner). Grill for 20 minutes, rotate packets (but never flip), and grill for another 20-25 minutes. Test the potatoes to make sure they are tender.
5) Open the packets by removing the top piece of foil from the packets. Add grated cheese to the potatoes. Cover grill and grill for another 10 minutes until cheese is very melted.
Serve potatoes while hot!