The night before coat lamb with mustard coating as follows; puree garlic into small bowl and mash to a paste with salt. Whisk in mustard, soy sauce, herbs, lemon juice and then oil to make a mayonnaise like cream. Coat roast and put it in the fridge overnight. To make the roast you will need; a shallow pan a rack an instant thermometer a sharp carving knife a napkin to hold meat as you carve Put on rack in pan on rack placed at the mid level in the oven preheated to 350 degrees. With the mustard coating you will need no basting the first 45 minutes. After 45 minutes strew the onion and the garlic into the bottom of the roasting pan. Sprinkle the rosemary on top of the vegies. After the roast has been in the oven for an hour, start checking the temp. leaving the instant thermometer in for a full 15 seconds for it to register. When the roast registers 130 degrees, take it out (it will continue to raise as the outside temp goes in. This will be medium rare.) Let roast sit out for 15 to 20 minutes before carving so juices can retreat back into the meat. Au Jus: While roast is resting, skim excess fat from roasting pan. Pour in a cup of light broth or dry white wine and bring to a boil-mashing vegies and scraping up brown bits. Pour into a saucepan and simmer several minutes skimming off any fat, correct seasoning. Just before serving, strain into warm saucebowl, pressing juices out of vegies and adding any new drippings from the roast. There will be just a small delicious spoonful to moisten each serving of lamb. Gleaned from Julia Childs thorough treatment of lamb and its cooking from book "The Way to Cook". For further info. see pp. 224 Submitted By MARY RIEMERMAN On 03-01-95 (1029)