Cut large, sprouted Kennebec potatoes into smaller pieces, the size of an egg. Each piece should have at least one sprout; two are better.
Leave the pieces in a dark place that remains between 60 and 65 degrees Fahrenheit to callus over. The area should be humid and well-ventilated. Leave the pieces for two days.
Rub the sprouts off the Kennebec potato pieces with your fingers. Cutting them may damage the potato and cause mold.
Place each piece into a slot in an egg carton, with the sprouted area pointing up.
Leave the egg carton in a place that remains at least 60 degrees Fahrenheit and is out of direct sun. Within six weeks, the potato pieces will sprout. When the sprouts reach 1 inch in height, plant the Kennebecs in the garden.