Preparation Whisk first 4 ingredients together in small bowl. Season dressing to taste with salt and white pepper. Using small sharp knife, remove peel and white pith from grapefruits. Working over large bowl to catch juices, cut between membranes to release segments. Squeeze juice from membranes into bowl. Reserve juice and segments separately. Trim base from endive heads and separate into spears. (Can be prepared 1 day ahead. Cover dressing, grapefruit juice and endive separately and refrigerate.) Place sliced radicchio on platter. Arrange endive spears in rows atop radicchio. Thinly slice avocados. Dip avocado slices into reserved grapefruit juice. Fill each endive spear with 1 avocado slice and top with 1 grapefruit segment. Whisk chopped fresh chives into dressing and drizzle over salad. Sprinkle with toasted chopped walnuts.
Preparation Whisk first 4 ingredients together in small bowl. Season dressing to taste with salt and white pepper. Using small sharp knife, remove peel and white pith from grapefruits. Working over large bowl to catch juices, cut between membranes to release segments. Squeeze juice from membranes into bowl. Reserve juice and segments separately. Trim base from endive heads and separate into spears. (Can be prepared 1 day ahead. Cover dressing, grapefruit juice and endive separately and refrigerate.) Place sliced radicchio on platter. Arrange endive spears in rows atop radicchio. Thinly slice avocados. Dip avocado slices into reserved grapefruit juice. Fill each endive spear with 1 avocado slice and top with 1 grapefruit segment. Whisk chopped fresh chives into dressing and drizzle over salad. Sprinkle with toasted chopped walnuts.