Scrub potatoes; with a mandoline or vegetable peeler, cut into 1/32-in.-thick slices. Place in a large bowl; cover with cold water. Soak for 30 minutes.
Drain; pat dry with paper towels. Place potatoes in a large bowl; drizzle with oil and toss to coat.
Arrange in a single layer in ungreased 15-in. x 10-in. x 1-in. baking pans. Bake at 400° for 18-22 minutes or until golden brown, turning once. Sprinkle with salt.
Meanwhile, in a small skillet, saute onion in oil until tender; cool to room temperature. In a small bowl, combine the yogurt, mayonnaise, green onions, seasonings and cooked onion. Serve with chips. Yield: 5 cups chips (1-1/2 cups dip).