In a 4-quart stockpot on medium heat, sauté the onions, celery and garlic with the grapeseed oil, salt, and pepper until the onions are translucent, 10 to 15 minutes. Add the carrots, potatoes, split peas, and chicken stock. Bring to a boil, then simmer uncovered for 40 minutes – 50 minutes, stirring often to keep the bottom of the pan from burning. Skim off the foam while cooking. Add the fresh oregano and blend with an emulsion blender to a creamy consistency. Taste for salt and pepper. Serve hot garnished with shaved parmigiano reggiano and a few splashes of Frank’s hot sauce.