Step 1

If your brisket is too large to sit flat on the bottom of your pressure cooker, cut it into pieces that will fit. Season brisket all over with salt and pepper. In an electric multi-cooker (such as an Instant Pot), set to searing mode or a stovetop pressure cooker set over medium-high heat, add oil and heat until shimmering. Working in batches, add brisket, and brown on both sides, about 6 minutes per side (the exact browning time will depend on your pressure cooker model; electric ones will generally take quite a bit longer than stovetop ones). Transfer brisket to platter or rimmed baking sheet, and set aside.

Step 2

Add onion, carrot, celery, and garlic, and season with salt. Cook, stirring and scraping up any browned bits, until vegetables are golden and have released most of their water and that water has cooked off, 25-35 minutes (the exact cooking time will again depend on the type of cooker you're using, with electric ones taking quite a bit longer); reduce heat at any point if vegetables threaten to scorch. The vegetables should have reduced significantly in volume by this time.

Step 3

Stir in ketchup and tomato paste and cook, stirring, until thick and sticky, about 3 minutes. Add wine and cook until reduced by half, about 5 minutes.

Step 4

Add thyme and bay leaves. Reduce heat to medium-low or turn off searing mode on electric multi-cooker. Give the vegetables a good stir, scraping the bottom well all over (this will be your last chance to stir before closing the cooker). Add brisket pieces, nestling them well in the vegetables, and add any accumulated juices. Seal pressure cooker and bring to high pressure over medium heat or using the pressure-cooking mode of an electric multi-cooker. Cook for at least 1 hour at high pressure and up to 1 hour 30 minutes. Choose 1 hour if your brisket pieces are closer to 1 inch thick, or if they're thicker but you want a little more chew to the meat; choose 1 hour 30 minutes if your brisket is closer to 2 inches thick, and you want it more tender.

Step 5

Rapidly release pressure cooker or allow to release naturally, then open. Transfer brisket pieces to a work surface, and let rest until cool enough to handle. Taste braising liquid and season with salt, if necessary. Discard thyme sprigs and bay leaves, and skim off any excess fat if it's there (this will depend on the cut of brisket). If the braising liquid is a little too watery, you can reduce it at this point by simmering it uncovered until it thickens slightly (in some electric multi-cookers, you may need to use the sauté or similar function).

Step 6

Slice brisket thinly against the grain. Arrange on a platter and spoon the sauce and vegetables all over, making sure the meat is bathing in juices. Cover and let stand for 30 minutes in a warm place. Serve.