Step 1Bring a small pot of water to a rolling boil. Add the onions and blanch 1 minute. Drain and cool, then slice off the ends and slip off the peel. Set aside.
Step 2Cut off the tops of the fennel bulbs and reserve 1 tablespoon of the green fronds. Wash the bulbs and trim off the root ends. Cut the bulbs crosswise into one-half inch slices. Set aside.
Step 3Heat the duck fat in a deep skillet over medium-high heat. Add the onions and cook, stirring constantly, 3 minutes. Add the fennel, carrots and salt and cook, stirring constantly, 2 minutes. Stir in the Aleppo pepper. Deglaze the pan with the stock.
Step 4Reduce the heat to low, cover the pan and cook 10 minutes or until the vegetables are tender. Stir in the maple syrup. Raise the heat again to medium-high and cook uncovered until the liquid is reduced to a glaze, a couple of minutes. Garnish with the reserved fennel fronds and serve.