White button mushrooms cook best when they're cut in order to help drive off excess moisture faster. Start by trimming away the bottom portion of each stem which will give them mushrooms more even stable shape. Decorate the mushroom for roasting or sauteing, hold the cap sideways on a cutting board. Place the tip of a sharp chef's knife or paring knife in between your fingers and thumb and cut down to split the mushroom. Without separating the halves rotate the mushroom slightly until you can comfortably and safely cut through at a 90-degree angle to the first cut. To slice mushrooms lay them flat against the cutting board with the stem side facing down. Hold the mushroom steady with your non-knife hand curling your fingers back slightly so that your first knuckles stick out. Using your knuckles as a guide make a series of parallel cuts slowly pulling your knuckles back at an even pace.