Add vegetable oil to instant pot and set to saute.: The pot should hiss gently when the oil is ready, not smoke. A shimmering surface indicates proper heat, which helps the ground beef develop deep browned notes rather than steaming. If the oil smokes, cancel saute and let it cool briefly to avoid burned flavors. Using the saute setting creates direct contact heat that jumpstarts caramelization.
Add ground beef and onion. Cook and crumble until ground beef is almost cooked through, about 5 minutes.: You will hear a steady sizzle as the meat hits the hot oil, and the aroma will shift from raw to toasty and savory. Keep the meat moving with a wooden spoon so it breaks into small crumbles that brown evenly; larger clumps trap moisture and lengthen cooking. If you see a lot of gray rather than brown, the pan is crowded or cool, so raise the heat slightly and spread the meat thin to promote browning. Browning builds fond, which is key for a flavorful base.
Add garlic, Worcestershire sauce, tomato paste, salt and pepper to pot. Cook for an additional 2 minutes.: At this stage you should smell the garlic bloom and the tomato paste begin to darken, producing a richer, slightly sweet scent. The Worcestershire sauce will add a tangy umami whisper. Keep stirring so the flavors meld and nothing clings and scorches. A common error is adding these too early and letting garlic burn, so add them after the meat has developed color.
Pour in 1/4 c. of beef broth and scrape the bottom of the pot to release any pieces of beef that may be stuck to the bottom of the pot. This will prevent the burn indicator on the instant pot when pressure cooking.: You want to see the browned bits lift from the stainless surface as you scrape, creating a glossy, flavored base. The small amount of liquid deglazes those bits, which then dissolve into the sauce. If you skip this, trapped browned pieces can trigger the burn notice, so don’t rush this cleanup step. The sound will change from a sizzle to a gentle hiss as the broth loosens the fond.
Add the rest of the broth and macaroni. Stir and make sure the macaroni is submerged into the broth.: The pot should look like a uniform pool of liquid with pasta beneath the surface. You might hear a soft glug as the broth settles and see pasta peeking under the surface. Ensuring the elbow macaroni is fully submerged prevents dry pockets and inconsistent cooking. If pasta floats, press it gently under the liquid; trapped air can cause uneven texture after pressure cooking.
Lock the lid, seal the valve and set the pressure cooking time to 5 minutes.: You will notice the pot building pressure with a low hum, and the float valve will lift when it is sealed. The short high pressure cooks the pasta quickly while allowing it to absorb flavor. Avoid opening the valve early, as sudden depressurization can lead to undercooked pasta. If you haven’t used a pressure cooker much, confirm the valve is set to seal to avoid steam loss during the cycle.
When instant pot is done cooking, quick release the steam valve. Stir in the cheese until completely melted and combined.: As you switch to quick release you will hear an eager rush of steam and a hissing sound that signals pressure dropping. Once safe to open, the lid reveals a bubbling, fragrant bowl. Stirring in the shredded cheddar cheese off heat creates a glossy, creamy coating; work quickly so the residual heat melts it smoothly. Avoid adding the cheese while the pot is still under pressure, which can cause the dairy to separate and become grainy. The final texture should be silky and cohesive, with a warm cheesy aroma.
