Using a mandoline, slice potatoes into very thin rounds (~1/8”).
Coat a “Mega-muffin” pan with PAM spray.
Place potato slices into the 6 muffin cups, layering overlapping slices and fill about half-way. Add spoonful of butter-cream mixture and top with Gruyère (use half) and some of the fresh chopped thyme.
Repeat with a 2nd layer of potatoes. Add another spoonful of sauce.
Place muffin pan on a baking sheet and bake for 45 mins.
Remove from oven and top each cup with the remaining Gruyère cheese. Bake for 15 mins more. Allow to cool and set before serving.