Cut the hamburger bun into 3/4 inch chunks and place them on a cookie sheet.

Place the cookie sheet in the oven and toast the croutons for 10 minutes. Set aside.

Place a medium skillet over high heat.

Add 1 teaspoon olive oil, and when hot, add the onions. Cook the onions until caramelized: stir frequently and adjust the heat so that they don't burn.

When the onions are a caramel brown color, add the vegetable stock and cook for another two minutes until the liquid evaporates.

Remove the onions from the pan to a plate and let them cool for 10 minutes.

When they are cool, place the eggs, water, salt and pepper in a bowl and whisk until the eggs are frothy.

Add the onions to the bowl and fold them into the eggs until well blended.

Place a small skillet over high heat and add 1 teaspoon olive oil.

When the pan is hot, add the egg mixture and cook for about 30 seconds.

Place the pan in the oven and bake the frittata for about 10 minutes, until the eggs are almost set but the center of the top of the frittata is still slightly liquid.

Sprinkle the croutons over the frittata and top with the provolone cheese. Return the pan to the oven to bake for another 3 to 5 minutes, until the cheese is melted.

Serve.