Begin by trimming the fennel bulb. Remove the green stalks at the top and set aside a small portion of the feathery fennel fronds for garnish later. Slice off the root end at the base of the bulb. If the outer layer feels thick or fibrous, peel it away using a knife or vegetable peeler. The interior of the fennel should appear crisp, pale, and juicy.

Using a mandoline slicer or a very sharp knife, slice the fennel bulb into paper-thin slices, cutting across the bulb from top to bottom. Thin slicing is crucial because fennel has a naturally firm texture. Delicate slices soften slightly and integrate better with the dressing and citrus.

Place the shaved fennel slices in a bowl filled with ice-cold water and allow them to soak for 10 minutes. This step removes some of the fennel’s natural bitterness and helps the slices curl slightly, making them extra crisp and refreshing. After soaking, drain the fennel thoroughly and pat dry with paper towels.

Using a sharp knife, slice off the top and bottom of each orange and the grapefruit so the fruit sits flat on the cutting board. Carefully cut away the peel and white pith by following the curve of the fruit. Once peeled, hold the fruit over a bowl and slice between the membranes to release clean citrus segments. This technique, known as supreming, produces tender, juicy segments without tough membranes.

As you segment the fruit, juice will collect in the bowl. Reserve 2 tablespoons of this fresh citrus juice, which will be used in the vinaigrette. The natural citrus juice adds depth and freshness to the dressing.

In a small bowl combine the olive oil, white wine vinegar, reserved citrus juice, Dijon mustard, honey, salt, and black pepper. Whisk vigorously for about 20 seconds until the dressing becomes smooth and lightly emulsified. The vinaigrette should taste bright, slightly sweet, and balanced with gentle acidity.

Rinse the arugula thoroughly under cold water and dry it completely using a salad spinner or clean towel. Dry greens are essential so the dressing coats the leaves evenly rather than diluting on wet surfaces.

In a large mixing bowl combine the drained fennel slices, citrus segments, and fresh arugula. Gently toss the ingredients together so they distribute evenly without breaking the citrus pieces.

Drizzle the citrus vinaigrette lightly over the salad. Toss gently using salad tongs until all ingredients are evenly coated.

Sprinkle the toasted sliced almonds across the salad and garnish with the reserved fennel fronds. The almonds add delicate crunch while the fennel fronds reinforce the aromatic fennel flavor.

Serve the salad immediately after dressing so the fennel remains crisp and the citrus stays fresh and juicy.