Cheesesteak Soup

Preheat the oven to 350°F. Wrap the sirloin in plastic wrap and freeze for 30 minutes. (This will make it much easier to slice thinly later!) 

In a medium bowl, toss the bread cubes with 1 tablespoon of the oil, ⅛ teaspoon cayenne, and a generous pinch of salt. Transfer to a baking sheet and bake, stirring occasionally, until golden and toasty, 10–11 minutes.

Heat 2 tablespoons of the oil in a large saucepan or braiser over medium heat until foamy. Add the flour and cook, stirring, until lightly golden, 2 minutes. Whisk in the broth and milk, raise the heat to high, bring to a boil, reduce the heat to medium-low, and simmer until the broth thickens, 2–3 minutes. Stir in the cheeses, mustard, 1 teaspoon of salt, and ¼ teaspoon cayenne, and then stir to incorporate. Season with more salt and cayenne. Press foil or parchment into the surface of the soup to keep warm and keep the top of the sauce from congealing.

Remove the steak from the freezer and cut against the grain into thin slices. Add sliced steak to a medium bowl, add soy sauce and fish sauce, and stir to combine. Set aside.

Heat a large skillet over medium-high heat, add 2 tablespoons of the oil, then cook the onions and peppers, stirring often, until charred and partially softened, 5 minutes. Transfer to a plate and cover to keep warm. Add the remaining tablespoon oil, then add the steak and cook, stirring occasionally, until caramelized slightly and cooked through, 3–4 minutes. Return the onions and peppers to the skillet, season with salt, and stir to incorporate.

Ladle 1 ¼ cups soup into each of 4 bowls, then divide the meat mixture among the bowls, garnish with parsley, and top with croutons.