Preheat your oven to 180 degrees (160 degrees fan-forced) and spray a 12-pan muffin tin with oil.
Cut the crusts off each slice of bread and, using a rolling pin, roll each slice until it is very thin.
Spread each slice with a smearing of Vegemite and press them gently into the the muffin pans.
Put the empty bread cases into the oven for 5 minutes, or until the edges are a little crispy.
Meanwhile, lightly beat the eggs in a small bowl together with the cream, chives and half of the feta.
Season with a pinch of salt and pepper.
Carefully pour the egg mixture into the bread cases (remember that the tray will be very hot) and top each tart with some diced tomato and the remaining feta.
Bake for 15 minutes or until the egg mixture has set.