Conservation: from 2 to 3 days in the vegetable compartment of the refrigerator. Preparation:  cut the base,  remove the sheets and  pass to water. TCut out the dimensions or  separate the heart into two. Cooking: 15 mns, plunged in salted ebullient water. Braised to accompany a roti. 10 mns with the pressure-cooker. Use: vintage, in sticks with salt or stuffed with roquefort or tapenade. Cut out finely and added to crumbs of crab or mixed salads .Cooked, braised,  as accompaniment  vegetable , condiment with the sheets in soups or sauces. With the furnace: to gratinate  20 mns 2 celery half-hearts (pre-cooked with the vapor), with  'bolognaise' sauce and Parmesan.