How to Make It
Preheat the oven to 350°. toast the chopped walnuts on a small baking sheet for about 7 minutes, or until fragrant. Let cool completely.
In a small bowl, combine the lemon juice, vinegar and grape juice. Stir in the oils. Season with salt and pepper and stir in the chopped mint.
In a large serving bowl, toss the radicchio with the endives, apples, grapes and toasted walnuts. Add the dressing to coat.