Chop the shallots, garlic, celery and sauté` together in a pan with 1 tbsp. olive oil for 3 minutes to soften. Splash in the white wine and evaporate. Add in the stock and mussels and bring to the boil. Place on the lid, reduce the heat and simmer for 5 minutes, shaking the pan occasionally. Strain the juices, transfer to another pan and reduce for 2 minutes before adding in the cream and 2 knobs of garlic butter. Meanwhile, slice the baguette, spread with the remaining 2 tbsp. garlic butter and grill until browned. Serve the mussels with the cream sauce and the bread on the side.