Storage Instructions

• Store the components separately.
• Refrigerate pot roast and gravy in airtight containers for up to 4 days. Store the cheese sauce separately and refrigerate for up to 3 days.
• Reheat the beef and gravy gently on the stovetop or in the microwave. Reheat the cheese sauce over low heat, adding a splash of milk if needed to loosen it.
• Once nachos have been assembled, they are best eaten immediately. Refrigerating assembled nachos will leave you with soft chips.
• For a party, keep the beef, gravy, and cheese sauce warm separately and assemble smaller batches of nachos throughout the event. This keeps the chips crisp and means guests aren't fighting over the last good corner of the pan.

Tips for Success

• Don't skip searing the roast. The browning isn't just for appearance. It gives the cooking liquid more depth, which ultimately makes your gravy better.
• Do not boil the cheese sauce. This is the step that can make or break this particular sauce. Evaporated milk gives you a very forgiving starting point, and the starch on the pre-shredded cheese helps stabilize the emulsion, but neither one can rescue a sauce that's overheated. High heat can cause the cheese proteins to tighten and the fat to separate, leaving you with a grainy or oily sauce instead of the smooth cheese sauce you're after. Use low heat, add the cheese gradually, and keep stirring. If the sauce does start to look slightly grainy, immediately remove it from the heat and whisk in a small splash of warm evaporated milk. Don't try to fix it by turning up the burner.
• Don't drown the chips. This is probably the biggest nacho mistake. Gravy and cheese sauce are delicious, but too much liquid turns tortilla chips into something closer to casserole noodles. Use enough to coat the nachos without soaking them.
• Drain the giardiniera. Especially when adding it to the cheese sauce. Excess oil can make the sauce greasy or interfere with its smooth texture. Drain it well and finely chop the vegetables before stirring them into the sauce.
• Taste your giardiniera before deciding how much to use. Giardiniera varies considerably in salt, acidity, oil, and heat. Start conservatively, especially if you're using a particularly spicy brand.
• Use pre-shredded cheese for this sauce on purpose. I almost always recommend shredding cheese yourself, and I still do for most recipes. But this is a deliberate exception. The anti-caking starch on pre-shredded Mexican cheese can serve the same practical purpose as the small amount of cornstarch traditionally used in this style of evaporated-milk cheese sauce. It helps stabilize the sauce without requiring an additional thickener. You can use freshly shredded cheese, but you'll want to add a small amount of cornstarch to achieve the same effect.
• Keep the heat low once you add the cheese. The evaporated milk should be hot before the cheese goes in, but the cheese itself should melt gently. High heat is the enemy of a smooth cheese sauce.
• Add the cheese gradually. Adding an entire bag of cheese to the pan at once can make it much harder to maintain a smooth emulsion. A handful at a time gives each addition a chance to melt evenly.
• Make the cheese sauce close to serving time. This sauce is best when freshly made and warm. If you need to make it ahead, reheat it very gently and loosen it with a splash of evaporated milk as needed.