Challerhocker Upside Down Gratin

Dairymaids get a little panicky when asked "what's your favorite cheese"? It's almost comparable to asking a mother to pick a favorite child. While it is a very tough decision to come to, we do have several favorites. And we are allowed to change our mind. This delicious and fragrant gratin features two of my favorites, Challerhocker and SarVecchio. It's assembled and baked upside down. Turning it over onto a plate may cause a little anxiety too, but it will be over quickly. This dish is pure heaven with a simple green salad and a nice Sauvignon Blanc.  

2 tablespoons Lucky Layla Golden Butter
6 springs thyme, plus more for garnish 
1 large sweet onion, sliced into 1/4 inch slices
1 lb Golden Yukon potatoes, peeled and sliced
1 tablespoon Calivirgin Extra Virgin Olive Oil 
1/3 lb Challerhocker, grated
1/8 lb SarVecchio, grated
sea salt and fresh cracked black pepper

Directions: 
Heat oven to 400. Melt butter in a 9 inch cast iron skillet over medium heat. Add thyme and onion and cook until fragrant, keeping onion slices intact. Toss potato slices with evoo, grated cheese and salt and pepper to evenly coat. Top the onion slices in the skillet with the potato mixture. Evenly distribute the potatoes and cheese into a even layer and gently press. Bake for 45 minutes or until golden brown and cooked through. Let cool and turn upside down onto a large plate, garnish with a bit of thyme and serve.