Poke a couple of holes into each potato and bake for 40 minutes.
Heat oil in sauté pan over med/high heat.
Add shallots and garlic and reduce heat to medium.
Add 2 cups sliced mushrooms and thyme.
Cook until mushrooms are soft (about 5 mins).
Drain excess liquid and set aside.
When potatoes have cooled so you can handle them cut in half lengthwise with a spoon.
Scoop out the inside of the potato leaving 1/8 inch of skin so it is still sturdy.
Add the inside of the potato to bowl along with mushroom mixture.
Add yogurt and 1 cup gruyere.
Mix well and add salt and pepper to taste.
Spoon the filling back into the potato skins and sprinkle with remaining cheese.
Place on baking sheet and return to 350°oven for 15 minutes.