Place potatoes in a large pot and cover them with 2 inches cold water. Bring to a simmer and cook until they are fork tender, 20–30 minutes. Remove from heat and set potatoes aside to cool. For the onion aderezo, in a large skillet, heat vegetable cooking oil over medium heat. Sauté onion, garlic, and ají amarillo. Stir until onion becomes translucent, about 5 minutes. Season with turmeric, stir for a minute, and then remove from heat. In a tall electric blender, puree the onion aderezo with milk and yogurt. Add saltines, mix in nooch, and continue to blend. Season with salt as needed. Peel the potatoes and slice them into 1/2-inch-thick rounds. Plate potato rounds on bed of lettuce, bathe with huancaína sauce, and top with olives.