If you're using fennel, quarter the bulb and leave the root attached so the pieces don't fall apart. If you're using leeks, use all but one of the leeks for the main braise, and set aside 1 small to medium one for the fried leek garnish.
Trim off dark & light green leaves off the leeks and save in your stock freezer bag. You really only want the white and very lightest green parts. Trim the hairy part off the root end and discard. Hold on to the root end and keep it intact while you cut the leek to clean it: holding the root end, stand the leek upright on a cutting board. Starting about 3/4 the way up the leek, slice down in half through the middle. Turn the leek a quarter turn, and slice again all the way down to the cutting board. Fan out leaves and rinse very well in cold water to get rid of any sand or dirt. Repeat for all the leeks (including the leek reserved for garnish).
Turn oven to 350. Add leeks and/or fennel to a roasting pan with a lid (can also use aluminum foil). Mix together the rest of the ingredients, and pour into pan on top of vegetables. Cover, and braise for 30 minutes. Remove lid and roast for 10 more minutes.
While the leeks and/or fennel are roasting, heat up your oil (to very hot) for making the fried leek garnish. Thinly slice the white part of the small leek (you should have a few tablespoons), and add to the oil. Fry till golden, remove from oil and sprinkle with salt.
Keep braised veggies in sauce till ready to serve. If making the day before, cool and store in sauce and reheat slowly over low heat on stove till heated through. If you were able to add the peppercorns in a small reusable tea bag or piece of cheesecloth tied up, remove it before serving. Remove the bay leaf as well. Serve leeks on a platter with a slotted spoon, and add the fried leeks on top.