2LargeSweet Yellow Onions or Spanish Onions, thinly sliced
6OzThinly Sliced Monterey Jack Cheese
1 1/2TspBalsamic Glaze
12Filet Medallions (1 1/2" thick)
1/2TspTurbinado Sugar or Light Brown Sugar
In a large skillet, heat 2 tablespoons of the oil over medium heat until it slides easily in the pan, 2 to 3 minutes.
Add the onions and cook, stirring occasionally so they don't stick to the pan, until they are soft and caramelized, about 20 minutes.
Spread the onions out over the surface of the pan. Remove from the heat and lay the cheese on top of the onions, letting it melt.
To make a jus, in a small saucepan, bring the stock to a simmer over medium heat. Remove from the heat and stir in the balsamic glaze. Cover the pan to keep the jus warm.
Season the meat on both sides with the salt and sugar.
In another large skillet, heat the remaining 2 tablespoons oil over high heat. Add half the medallions, or as many as will fit in a single layer, and sear them until they are caramelized, 1 to 1 1/2 minutes per side.
Cook the remaining medallions in the same way, adding more oil and letting it get hot before adding the meat to the pan. Meanwhile, without opening them, toast the baguettes so that the outsides, top and bottom, are hot and crispy.
Halve the baguettes horizontally, leaving them hinged on one side. To assemble the sandwiches, lay 3 medallions on the bottom of each baguette. Top with the onions and cheese, dividing them equally among the sandwiches.
Drizzle 1/4 cup of the jus on the inside top half of each baguette. Close up the sandwiches and you're good to go.