Slice the fennel thinly using a sharp knife or mandolin slicer and place it in a large salad bowl.

Peel the pink grapefruit, segment it by slicing alongside the membranes, and add to the bowl.

Cube the avocado, remove the pit, and add the chunks to the salad bowl.

Incorporate lightweight greens into the bowl with fennel, grapefruit, and avocado, mixing gently.

In a small jar, combine grapefruit juice, olive oil, white balsamic vinegar, shallots, and mustard; shake until emulsified.

Drizzle the dressing over the salad, season with salt and pepper, and toss gently to coat.

Garnish by shaving fresh Parmesan cheese over the top before serving.