In a large bowl combine the ingredients for the meatballs, using your hands or a wooden spoon to combine. Form into about 24 meatballs about 1 – 1 1/2 inches in diameter. Place on a plate until ready to use.: The aroma of raw beef , onion , and Parmesan cheese mingling is upfront and slightly sweet, and when you press the mixture gently it should hold shape without feeling dry. This tactile check is important because it tells you whether the Italian bread crumbs have absorbed enough moisture; overly wet mix will fall apart, overly dry mix will produce dense meatballs. I usually test one small ball by frying it briefly to confirm seasoning and texture before shaping the rest. A common mistake is overmixing, which makes the meatballs tough, so mix just until combined and stop. The visual cue is a cohesive surface that still looks slightly loose before forming into uniform balls, about the size of a ping pong ball.
Set the Instant Pot to the saute setting. Add olive oil to the pot. When it’s hot place the meatballs in Instant Pot, you may need to work in batches, and cook until all sides are brown, rotating as they cook. Remove meatballs from Instant Pot when they are browned and set aside.: The sizzling sound as the olive oil hits the pot is immediate, and you want a steady sizzle rather than furious spitting. Browning creates deep, caramelized flavors that will dissolve back into the sauce, giving complexity you cannot get without this step. Work in batches to avoid overcrowding, which traps steam and prevents browning; each meatball should show golden brown patches all around before turning. Use tongs to rotate them gently so they keep their shape. A typical error is rushing this step and crowding the pot, leading to pale, steamed meatballs instead of browned ones. The visual cue is a rich mahogany color on multiple sides, and the pot should have browned bits clinging to the bottom, which you will use in the next step.
Stir in beef broth while IP is still on saute setting, deglazing the bottom of the pot to loosen about bits of meatballs to prevent burn warning.: When you pour in the warm beef broth it should hiss gently and lift those fond bits from the bottom, turning them into a flavorful base for the sauce. Stir with a wooden spoon, scraping the bottom until you see the pot clear of dark stuck-on pieces, because trapped residue can trigger the burn warning during pressure cooking. The aroma becomes richer and slightly roasted as those browned fragments dissolve into the liquid. One pitfall is adding cold liquid and not scraping properly, which can leave stuck bits and risk an error; use warm broth and vigorous scraping. The pot will smell meaty and savory, a clear sign you’ve rescued all the concentrated flavors into the cooking liquid.
Then place meatballs back in the pot, add spaghetti making sure it’s spread evenly out and not in clumps to prevent them from sticking together. Then pour the pasta sauce and diced tomatoes on top.: Layering is visual and tactile, and spreading the broken spaghetti in a single even layer prevents overlapped clumps that cook unevenly. As you nestle the meatballs back in, you will feel the pot filling but not packed. Pouring the pasta sauce and petite diced tomatoes on top creates a tomato blanket that steams the noodles beneath. The mixture should look evenly distributed with no big dry pockets. A common mistake is stirring the noodles in dry, which can cause them to clump; instead, leave them spread and pour liquids gently so everything cooks uniformly. The sound will be quiet bubbling as liquid settles around the pasta, and the appearance should be saucy and cohesive.
Put the lid on the pot and set the steam release knob to the sealing position.: As you close the lid you will hear the valve click into place, giving a sense of finality. The sealing position traps steam efficiently so pressure can build, which is essential for even cooking. Make sure the rubber gasket is seated and nothing is obstructing the vent, because a poor seal will prevent pressure buildup and lead to undercooked spaghetti . A mistake I sometimes see is neglecting to check the seal; if you have trouble sealing, open and reseat the lid and gasket. The visual cue here is that the valve remains down, indicating a proper seal until pressure begins to form.
Press the manual button and adjust to 8 minutes on high pressure.: When the cooker ramps to pressure you will hear a deepening sound as steam accumulates, and the timer will begin its countdown once full pressure is reached. This timing gives the spaghetti enough time to hydrate thoroughly while the meatballs finish cooking through. The why is simple, pressure cooks rapidly penetrate ingredients so textures meld without prolonged simmering. An error to avoid is setting too high a time, which can overcook pasta into mush. The correct cue is a steady, low hum from the pot and the timer counting down after the float valve pops up, signaling pressure is established.
After the cook time has finished, turn off the pot and do a quick release of steam.: Releasing steam quickly makes the pressure drop fast so you can open the lid and check the dish, and the first burst of steam carries rich tomato fragrance that fills the kitchen. Use a long utensil and keep your hand clear when flipping the steam release to vent, because hot steam will blast upward. This technique stops carryover cooking of the spaghetti , helping it retain a better texture instead of becoming overly soft. A common slip is attempting to open the lid before the float valve drops; always ensure the pressure is fully released and the valve has returned down. When you lift the lid, the sauce will steam and you will see plump noodles and glossy meatballs nestled in sauce.
Serve immediately.: The final sensory reward is the warm plate, the steam that curls off the sauced spaghetti , and the first bite combining tender meatball interior with tangy sauce. Serve right away so the texture stays ideal, and if you like a finishing sprinkle of Parmesan cheese add it table side for freshness. A common mistake is letting the pot sit closed too long, which can make noodles overly soft from residual heat; plating promptly preserves the intended mouthfeel. The visual sign of readiness is glossy sauce clinging to each strand and meatballs with moist, slightly springy centers.
