Combine the red wine, bay leaf, thyme and rosemary in a saucepan and bring to a boil.
Wash the potatoes and boil them in salt water for about 15 minutes with their peel still on. Take the potatoes out of the water, halve them and brown them in a frying pan with a little oil and thyme.
To make the celeriac purée, peel and dice the celeriac. Boil it in a stockpot. Add the milk and boil until the celeriac is soft. Strain the milk and pour the mass into a stockpot. Add the diced butter and salt. Purée into a smooth cream with a handheld blender.
Season the steaks with salt and pepper. Sear in a little oil on both sides. Leave in the oven at about 175 degrees for 4–8 minutes, depending on the desired doneness.
To serve, scoop a spoonful of celeriac purée onto a plate, place a steak on top and serve with a few small potatoes and the red wine sauce.