How to Make It
In a microwave-safe bowl, cover the porcini with 1 cup of water. Cover and microwave at high power for 1 minute, until the mushrooms are just softened. Drain, reserving the soaking liquid. Rinse and chop the mushrooms.
In a large skillet, heat 2 tablespoons of the oil. Season the veal with salt and pepper and dust with the flour, tapping off any excess. Add half of the veal to the skillet and cook over moderate heat, turning once or twice, until browned, about 8 minutes. Transfer the veal to the pressure cooker. Repeat with the remaining 2 tablespoons of oil and veal.
Add the carrot, onions, garlic, sage and porcini to the skillet and cook over low heat until slightly softened, about 2 minutes. Add the wine and vinegar and scrape up any browned bits stuck to the pan. Scrape the mixture into the pressure cooker. Add the stock and 1/2 cup of the porcini soaking liquid, stopping before you reach the grit at the bottom. Season lightly with salt and pepper and bring to a boil.
Cover and close the pressure cooker according to the manufacturer’s instructions. Cook at moderately low heat, maintaining high pressure for 25 minutes. Gently release the pressure by depressing the valve or by running cold water over the top. Transfer the ragù to a bowl and serve over polenta, noodles or crusty bread.