Preheat the oven to 400 degrees F. Place the potatoes on a baking sheet and pierce them a few times with a fork, all over. Roast the potatoes for 50 to 60 minutes, until they are soft enough to cut through.
While the potatoes are roasting, caramelize the onions. Heat a large pot over low heat and add 1 tablespoon of butter and the olive oil. Add in the onions with a sprinkle of salt. Cook, stirring occasionally, untilt the onions are caramelized - about 50 to 60 minutes. Make sure they are over the lowest heat so they don’t burn. In time, they will caramelize themselves without any sugar! If you’re in a rush, you can add a few teaspoons of brown sugar or honey to help them along.
Slice the potatoes down the center and sprinkle with the gruyere cheese. Add a sprinkling of the dried thyme. Stick the potatoes bake in the oven for 5 to 10 minutes, just so the cheese melts.
While the cheese melts, heat a small skillet over medium heat and add the remaining tablespoon of butter. Add in the garlic and cook for 30 seconds. Add in the rest of the thyme and bread crumbs and stir to coat, tossing for 5 to 6 minutes are they brown.
Remove the potatoes and top with the caramelized onions. Sprinkle on the the bread crumbs. Add a dollop of yogurt or sour cream and a few fresh chives. Devour!