If kale is your go-to leafy green because of its high calcium content, you'll swoon over stinging nettle, which boasts four times the calcium at 428 mg of calcium per cup, according to the U.S. Department of Agriculture. Nettles are also rich in vitamins A, C and K, iron, potassium, protein and more, making them an ideal food to add to any meal.
Related: Learn how Pacific Northwest tribes relied on nettle as a fortifying early-spring food.
Cook nettle in boiling water for 5-10 minutes. Drain well; save broth. Puree nettle in blender or food processor; set aside.
Saute onion in oil until golden. Add flour and cook, stirring for 2 minutes. Slowly add 1/2 cup nettle broth or milk and cook, stirring often until dry and thick. Add a little of this at a time to the beaten egg yolk, until they are well mixed. Now stir in nettle puree, salt and cheese.
Last, carefully fold in egg whites. Put in a souffle dish or carefully spoon into ramekins. Bake in a water bath at 350 degrees until firm, 30-40 minutes.