Peel peaches and cut them into 1 inch cubes. Grind mustard seed briefly in a spice grinder until cracked but not powdered. In a 9 or 10 inch non-reactive skillet, stir peaches with all remaining ingredients. Cover and cook over low heat, stirring occasionally to prevent sticking, for about 1 hour, or until peaches are very soft and liquid is the thickness of sour cream. Remove from heat and puree in a food processor or blender. Let cool. If not using immediately, pour into a clean, dry jar or bowl, cover tightly and refrigerate for up to 3 weeks. If you wish to store mustard longer than 3 weeks, sterilize 2 half-pint canning jars by washing and rinsing them in a dishwasher without detergent; keep them warm in a 250 degree oven. Pour boiling water over the jar lids to soften the rubber seals; cover with a towel to keep warm. Pour sauce into hot jars. Wipe rims carefully and seal with hot lids and metal bands. Place jars on a rack, without touching, in a large, deep pot with water to cover them by one inch. Cover and boil for 15 minutes. Use tongs to remove jars to a cooling rack and allow to cool to room temperature and then check seals. Jars are sealed when center of the lids is slightly indented and cannot be pressed in with a fingertip. Store at room temperature. Makes 2 cups. Use this mustard as a coating for roast meats, grilled meats or cold cuts and on skinless chicken before grilling. You can also incorporate it into vinaigrettes. Recipe from "Summer Fruit" (Collins, $19.95). Typed by Lynn Thomas dcqp82a.