Preheat the oven to 375 degrees F.
Grease a 9x13" baking dish.
Thinly slice your potatoes. I use a mandolin to do this so my slices are super thin.
In a medium skillet, heat the butter over medium heat.
Once melted, add the garlic and cook for 1 minute.
Add the flour and whisk to combine with the butter and cook another minute.
Slowly whisk in the cream, season with salt and pepper, and let it cook 4-5 minutes to thicken slightly.
Remove from heat and add in the blue cheese, stirring to combine.
Layer ¼ of the sliced potatoes on the bottom of your baking dish.
Top the potatoes with approximately ¼ of the blue cheese cream sauce and ⅓ cup of shredded Parmesan cheese.
Repeat this with four layers of potatoes, ending with the remaining Parmesan cheese.
Cover with foil and bake for 35 minutes. Uncover and bake an additional 35-45 minutes, or until the potatoes are tender.
Serve topped with fresh thyme. Enjoy!