Heat 1 tablespoon walnut oil in a medium skillet. Add ham, walnuts, and garlic. Sauté 10 minutes. Add sherry vinegar, stir well. In a large bowl, toss ham mixture with potatoes, additional 2 tablespoons walnut oil, red pepper, green onions, salt and pepper. Serve warm or cold with grilled steak, burgers, chicken or fish.