Make the Dressing: Combine the sherry vinegar, dijon mustard, onion powder and minced garlic in a bowl. Whisk together then slowly drizzle in the avocado and olive oil while whisking rapidly. The dressing should have a creamy consistency. Season with salt and pepper and refrigerate until needed.
Cook the Chicken: Preheat the oven to 350˚. Heat a saute pan on medium high heat. Season the chicken with salt and pepper, add the avocado oil to the pan and sear the chicken on both sides until golden brown, about 4 minutes per side. Transfer to the oven and cook until the chicken is 165˚, about 8 minutes.
Toast the Pine Nuts: While the chicken is roasting, place the pine nuts on a small baking sheet and toast in the oven for 10-12 minutes, until golden brown, giving them a stir every 5 minutes.
Pickle the Onions: Slice the onions as thinly as possible. Place them in a bowl and add the sherry vinegar and a ½ teaspoon of salt. Combine well and let sit for 10 to 15 minutes. They will soften and turn pink.
Cook the Potatoes: Place the potatoes in a pot and cover with cold, salted water. Bring to a boil then reduce the heat to a simmer and cook uncovered until the potatoes are fork-tender, about 12-16 minutes, depending on their size.
Cook the Peas: Trim the ends and remove the string if it’s fibrous. Fill a small mixing bowl with cold water and ice cubes. Bring a pot of salted water to a boil and cook the peas for 2-3 minutes. They should be bright green and still slightly crunchy. Drain from the boiling water and submerge in the ice water. Once they are cold, remove them from the water.
Make the Salad: Slice or shred the chicken. Combine with the lettuce, feta cheese, pine nuts, pickled onions, potatoes and peas. Toss with your preferred amount of salad dressing, check for seasoning and enjoy. The salad and dressing can be prepared ahead of time, but only add dressing to the salad once you’re ready to serve it.