1. Mix ground beef with onion soup mix; set aside.
2. Heat a large skillet over medium-high heat, add butter. When melted and hot, add the onions, pinch of thyme, and 1/4 cup of water. Cover with a lid and allow to simmer/steam for three or four minutes until onions are tender and the water is nearly evaporated. Remove lid and continue to cook, stirring often until onions are soft and beautifully browned, add a tablespoon of the brandy, after a minute remove the pan from heat; set aside.
Shape burgers. Cook on the stovetop in a medium-hot skillet or on the grill over medium-high heat, until burgers are done to your liking. Add a spoonful of caramelized onions and a slice or two of cheese to the top of each burger. Cover with a lid for a minute or two to get the cheese to melt.
In the meantime, under broiler or grill toast buns. Assemble burgers and enjoy!
Recipe adapted from the blog Frugal Hausfrau