Grease or butter 6 mini ramekins. In a small sauce pan combine; butter, heavy cream, thyme sprigs whole, minced garlic, ground nutmeg, salt, pepper, and the shallot peeled and cut in half.
Mix together and heat over medium-high heat to bring just under a boil. Once bubbling, simmer 15 minutes on low.
As the cream sauce is simmering, peel your sweet and golden potatoes. Slice into thin disk. You can slice the disk in halves or 1/4 for small pieces.
Start layering your greased ramekins. Start with one layer of sweet potatoes, then a layer of golden potatoes, then a layer of parmigiano-reggiano. Repeat layers until you have reached the top. Finish top off with a small bit of cheese.
Strain your cream sauce in a bowl or measuring glass. So you keep the cream sauce and discard the large sprigs and shallot. Evenly pour the cream sauce over the 6 dishes.
Bake for 35 minutes until golden and bubbly. Top with fresh thyme and a sprinkle of nutmeg. Enjoy!!