Instructions

1. Heat a heavy bottomed saucepan over medium heat. Add in onions and 1 tablespoon olive oil. Cook for 1 minute until heated through, then turn heat down to low and add in 1/4 cup water, remaining 1/4 cup olive oil, and salt.
2. Cook, stirring occasionally, for 1 hour. The onions will go from white to translucent, and finally will begin to turn golden brown. If the onions are looking dry, add 1-2 additional tablespoons of water, as necessary.
3. Once onions have reached a nice medium golden brown color, remove from heat and allow to cool slightly. Onions can be stored for up to 1 week in the fridge.
4. To make the grilled cheese, heat a skillet over medium heat. Spread mayonnaise over both slices of sourdough, then spread Maille Old Style Whole Grain Dijon Mustard over the opposite side of one of the slices. Place both slices, mayo side down, onto skillet.
5. Dollop the mustard slice of bread with caramelized onions and a sprinkle on few leaves of fresh thyme. Carefully place grated gruyere over the other slice. Cook for 2-3 minutes, until cheese is melted completely.
6. Press sandwich together, cut on the diagonal, and serve!