How to Make It
Preheat the oven to 350°. Line a large baking sheet with parchment paper. In a small skillet, melt 1 tablespoon of the butter. Add the chopped onion, season with salt and pepper and cook over moderate heat until softened but not browned, about 4 minutes.
In a medium saucepan, combine the cream cheese, Jarlsberg and dehydrated onions. Set the pan over simmering water and stir until melted. Remove the cheese mixture from the heat and stir in the remaining 7 tablespoons of butter along with the chives and sautéed onion.
Beat the egg whites until they hold stiff peaks. Stir one-quarter of the egg whites into the warm cheese mixture, then fold in the remaining whites. Dip the bread cubes into the cheese mixture, a few at a time, coating them thoroughly.
Transfer the cubes to the prepared baking sheet. Bake for 15 minutes, or until the puffs are golden. Serve hot.