Heat oven to 350 degrees. Slice pork roast down its center lengthwise; cut to within 1 inch of the bottom without cutting through. On each side of the center cut, slice two ½-inch-wide “pages” lengthwise; cut to within 1 inch of the bottom without cutting through. Rub lingonberry jam on pages and center cut. Pit and slice avocado into ½-inch pieces and place between pages. Roll meat, and tie gently but firmly with butcher’s twine. In a large heavy skillet over high heat, melt butter and saute garlic about 1 minute. Add pork roast and sear to golden brown on all sides. Remove to a roasting pan, reserving the pan with drippings. Roast 45 minutes or until a meat thermometer reads 150*. Cover with foil and let rest. Return pan with drippings to high heat, add wine, and scrape up any stuck-on bits. Whisk in cream, then flour, then herbes de Provence. Slice pork into ⅛-inch-thick pieces. When you lay slices on a plate, they should look like a tree with green and red leaves. Ladle sauce over slices.