Slice the potatoes into thin slices. Place them in a large mixing bowl and toss together with jalapenos, Parmesan cheese, chili powder, salt, pepper, garlic, and heavy cream.
Pour potatoes into a slow cooker. Cover with lid and cook on high 3-4 hours, or low for 7-8 hours.
During the last hour of cooking, sprinkle cheddar cheese over potatoes. Cover and continue cooking for the remaining hour.