Finely chopped lemon mixed with grainy mustard, sugar, and olive oil makes a stellar dressing for this radicchio-and-mint salad.
Tear radicchio into bite-size pieces; soak in ice water 20 to 30 minutes. Drain well and spin dry.
Meanwhile, using a sharp knife, remove peel and pith from lemon. Quarter lemon lengthwise and discard center membrane and seeds; finely chop. Place in a large bowl, and stir in mustard,sugar, and oil to combine. Season with salt and pepper. Toss radicchio and mint with dressing, season with salt and pepper, and serve.
Soaking the radicchio in cold water helps curb the leaves' naturally bitter edges.