Put eggs in a pot and add water, enough to cover the eggs by about 2 inches. When water comes to a boil, lower the heat to a simmer and cook for 12 minutes. When cooked, drain the hot water and add cold water to quickly cool the eggs. Use the back of a spoon to gently crack the shell of the eggs. The more cracks you make, the more intricate the “marbling” in the final product. (Do not peel the shell.)