Slice all the onions into thin wedges (I used 8 onions) and pile them on top of two sticks of butter in a saute pan on medium high heat. Coat all the onions in the melted butter as it melts.
Let the onions sizzle until browning appears. Using a nonmetal spatula, scrape the bottom of the pan. When scraping becomes difficult or resistant, splash with white wine to ease the dislodging of the brown bits. Repeat every 15 or 20 minutes, lowering the heat as the browning begins. This could last for at least an hour. Drink wine.
Preheat the oven to 375 and place the pastry squares on a parchment lined baking sheet.
Score the edges of the pastry to make an inner square without cutting the pastry all the way through.
Pile about a tablespoon of bleu cheese (more or less) inside the scores and follow with a heaping tablespoon of carmelized onions, using the back of the spoon to flatten out the mixture slightly to the inside of the scores.
Brush the outer edges of the pastry with the egg.
Bake for about 30-45 minutes or until the edges are browned. Serve immediately! With wine! And for the love of all things delicious....save your extra carmelized onions.