Raw foie gras can be roasted, sauteed, pan-seared ("poêlé") or (with care and attention), grilled. As foie gras has high fat content, contact with heat needs to be brief and therefore at high temperature, lest it burn or melt. Optimal structural integrity for searing requires the foie gras to be cut to a thickness between 15 and 25 mm (½ – 1 inch), resulting in a rare, uncooked center. Some chefs prefer not to devein the foie gras, as the veins can help preserve the integrity of the fatty liver. It is increasingly common to sear the "foie gras" on one side only, leaving the other side uncooked. Practitioners of molecular gastronomy such as Heston Blumenthal of The Fat Duck restaurant first flash-freeze foie gras in liquid nitrogen as part of the preparation process.