Melt three tablespoons clarified butter in a skillet over a medium flame. Toss peeled and thinly sliced shallots into the skillet and fry in butter until fragrant.
Add coarsely chopped Swiss chard and thinly sliced potatoes into the skillet and continue to cook until the Swiss chard wilts and the potatoes are tender when pierced by a fork.
Beat one dozen pastured eggs with three tablespoons heavy cream until the mixture becomes uniform. Season the eggs to your liking with salt and black pepper.
Reduce the flame to medium-low then pour the beaten eggs and cream into the skillet, over the vegetables. Cook over medium-low until barely set, about six minutes or so.
Place the frittata in your oven, under the broiler for about six minutes until it is cooked through.