Combine buttermilk, Feta and garlic in a blender container. Blend on high for 1 minute until smooth and creamy. Transfer to a medium size bowl.
Whisk in Greek yogurt until smooth. Add mustard, lemon juice and lemon zest and stir to incorporate.
Drizzle in olive oil in a steady but very slow stream. Don't try to drizzle the oil in too fast or dressing will come out very thin. As you slowly add the oil, the dressing is emulsified, which means the oil and the buttermilk/yogurt mixture become one.
Add fresh herbs and stir to combine. Take a taste and add salt and freshly ground pepper as needed.
For the walnuts, preheat oven to 350˚F. Combine walnuts, olive oil, honey and a pinch of salt in a small oven-safe pan. Bake for 8-10 minutes or until golden, stirring every 2-3 minutes. I recommend using a timer. Watch carefully as they can go from golden to burnt in a heartbeat. Set aside to cool, stirring occasionally to keep nuts from sticking to pan.
For the salad, place a handful of arugula in the bottom of four shallow bowls. Arrange berries, avocado, chicken, shallot or red onion and more arugula in sections. Add a scoop of candied walnuts in the center of each salad. Drizzle each salad with dressing or pass dressing at the table.