Vegemite is an Australian spread similar to British Marmite. It's a vegetable and yeast extract with a saltier, more pungent flavor than its cousin, with notes of malt barley.
Vegemite is said to be an acquired taste, but Australians have been pairing this beloved spread with cheesy dishes for years, and just a bit makes your mac and cheese fantastic.
Vegemite works particularly well with cheddar mac and cheese, since the cheddar can stand up to the flavor, but also pairs well with milder mozzarella or Swiss cheese sauces.
Start by incorporating 1 tablespoon of Vegemite into your cheese sauce. The spread is salty, so reduce your quantities of other salty ingredients and taste as you go.