1/3 cup sour cream
1/3 cup plain whole-milk Greek yogurt
1 tablespoons plus 1 1/2 tespoon sherry vinegar or apple cider vinegar
5 garlic cloves, 1 finely grated, 4 crushed
1 teaspoon honey
8 tablespoons Arbequina Extra Virgin Olive Oil from Olive Oil Etcetera, divided Kosher salt
2 scallions, thinly sliced
1/2 cup panko (japanese breadcrumbs)
2 medium radicchio, preferably Castelfranco, leaves separated
Mix sour cream, yogurt, vinegar, grated garlic, honey, and 5 tablespoons olive oil in a small bowl; season dressing with salt.
Heat remaining 3 tablespoons of oil in a medium skillet over medium heat. Add crushed garlic and scallions and cook, stirring often, until golden brown around the edges, about 4 minutes. Add panko and season with salt. Cook, stirring often, until golden brown, about 3 minutes. Finely grate lemon zest directly into pan and toss a few times to incorporate. Transfer breadcrumbs to paper towels to drain; let cool. Taste and season with more salt if needed.
Place radicchio in a large bowl. Drizzle with dressing; toss gently to coat. Season with salt and scatter breadcrumbs over.
Note: Dressing and breadcrumbs can be made 2 days ahead. Cover and chill dressing. store breadcrumbs airtight at room temperature.