Pat ribeyes dry with paper towels, season with salt and pepper on both sides and allow to come to room temperature, about 30 minutes.
Place sous vide immersion circulator in water and set to 10 degrees lower than target doneness temperature.
Place both ribeyes in one sous vide bag, along with 1 T. butter and 1 garlic clove; vacuum seal bags and cook for 2 hours.
Remove steaks from sous vide bag and pat dry with paper towels.
Place olive oil in cast iron pan set over high heat. Place ribeyes in pan for a hard sear.
Add 2 T. butter, remaining garlic clove, and remaining sprig of thyme to pan. Flip steaks and baste until golden brown. Remove from pan and set steaks on wire rack lined baking sheet. Top steaks with Parmesan crumble.
Preheat oven broiler to high. When broiler is preheated, place baking sheet with steaks approximately 5” from heating element and broil until crust is golden brown, about 2 to 3 minutes.
Set steaks aside until ready to plate.