Place the green beans in a microwave safe bowl along with 2 Tbsp water. Cover and microwave for 7 minutes to cook and soften.
Preheat your oven to 350 degrees F
Place one tablespoon of the butter in a large cast iron skillet or oven safe saute pan along with the mushrooms and saute over medium high heat until the water has evaporated form the pan and the mushrooms begin to brown.
Add the remaining butter, heavy cream, thyme and black pepper and stir.
Add half the cheese and stir until it begins to melt into the mushroom mix.
Add the green beans to the pan and stir into the sauce.
Remove the pan from the heat and sprinkle the beans with the remaining cheese. Place the pan in the preheated oven and bake for 15 minutes or until the cheese begins to brown on top. Serve hot.