The ancient Vikings had their own unique way of tempering chocolate in their kitchens. They used a built-in chocolate tempering machine made of iron. This machine consisted of an iron pot with a wooden handle and a spout. The Vikings would heat the chocolate in the pot and then pour it through the spout while stirring with the handle, achieving the desired temper. This ancient kitchen innovation allowed the Vikings to enjoy rich and perfectly tempered chocolate in their desserts and sweet treats.