In a medium skillet cook leeks in the 1 tablespoon olive oil til tender; remove from heat.

In a blender container or food processor boel combine parsley, thyme, Parmesan or Romano cheese, salt and pepper. Cover and blend or process with several on-off turns till finely chopped. With the machine running, gradually add the 3 tablespoon oil; blend or process to consistency of soft butter. Add leeks and nuts; process with several on-off turns till coarsely chopped. Set aside.

Remove fat and paper-thin membranes from surface of tenderloins. Use a sharp knife to cut each tenderloin lengthwise to, but not through, opposite side. Cover one tenderloin with clear plastic wrap. using the flat side of a meat mallet and working from center to edges, pound the tenderloin to a 12x8-inch rectangle. Remove wrap; repeat with the remaining tenderloin.

Sprinkle tenderloins lightly with additional salt and pepper. Spread half the parsley mixture evenly over each tenderloin to within 3 cm of edges. Roll up each tenderloin from a short side. Tie rolls with string, if necessary. Insert a meat thermometer in center of one tenderloin. Place meat, seam side down, on a rack in a shallow roasting pan.

Roast, uncovered, in a 325� oven for 45-60 minutes or till thermometer reads 160�. Cool about 30 minutes at room temperature. Remove string; cut into slices about 1 cm thick. Cover and chill. Serve with Roasted-Garlic Mayonnaise.

Roasted-Garlic Mayonnaise: Peel away outer skin from 1 medium head garlic. Cut off the pointed top portion with a knife, leaving the bulb intact but exposing the individual cloves. Place in a small baking dish; drizzle with 2 tsp olive oil. Bake, covered, alonside the meat, for 45-60 minutes or till cloves are very soft. Cool slightly. Press to remove garlic "paste" from individual cloves. Mash garlic with tines of a fork. Stir together garlic paste and half cup light mayonnaise dressing or salad dressing. Thin mixture with a little milk, if necessary. Cover and chill till serving.