Instructions
Step 1
In a small bowl, cover the raisins with lukewarm water. Set aside until plump, about 20 minutes. Drain and set aside.
Step 2
To a large skillet over medium heat, add 1 tablespoon of the oil. When it’s hot and shimmering, add the onions and cook, stirring occasionally, until lightly browned, about 12 minutes. Add the vinegar, pine nuts, sugar, and reserved raisins, stirring to coat. Working in batches, add the radicchio and cook, turning occasionally with tongs, until the radicchio is thoroughly wilted but retains a little bite, 10–12 minutes.
Step 3
Remove the skillet from heat, drizzle with the remaining oil, and season to taste with salt, black pepper, and more sugar if needed. If enjoying as antipasto, transfer to a large platter and serve. If serving as cicchetti, cut the larger radicchio leaves into smaller bites, divide among the ciabatta slices, and serve.