Season the meat on all sides with 2 1/2 teaspoons of the salt and 1 teaspoon of the pepper. Dredge the veal shanks in the flour, shaking them to remove any excess. Set the shanks aside. Reserve 3 tablespoons of the remaining dredging flour and discard the rest.

Heat the olive oil in a 6-quart pressure cooker set to the “browning” program. Brown the shanks on all sides, in batches if necessary, 10 to 12 minutes per batch. Remove the shanks from the pressure cooker and set aside.

Add the onion, celery, and carrot to the pressure cooker and cook until softened and lightly browned around the edges, 4 to 6 minutes. Add the tomato paste, garlic, bay leaves, half of the thyme, half of the rosemary, the remaining 1 1/4 teaspoons salt, and the remaining 1 teaspoon pepper. Cook, stirring, for 2 minutes. Add the red wine, scraping the bottom of the pan to loosen any browned bits. Add the stock and return the shanks to the pressure cooker. Bring to a boil. Close and lock the lid, and set to “high pressure” for 65 minutes.

Open the pressure release valve and allow the steam to escape. Unlock and carefully open the lid. The shanks should be nearly fall-from-the-bone tender. If the meat still meets with resistance, continue to cook under pressure for 2 to 4 minutes longer. Carefully transfer the shanks to a bowl and tent it with aluminum foil to keep warm. Remove and discard the bay leaves.

In a medium heat-proof bowl, mix the butter with the reserved dredging flour to form a smooth paste. Ladle 1 cup of the hot cooking liquid into the bowl and whisk to combine. Then stir this flour-broth mixture into the cooking liquid in the pressure cooker. Add the remaining rosemary and thyme. Set the pressure cooker to the “simmer” program and cook, stirring occasionally, until the sauce is thickened and smooth and any floury taste is gone, 5 to 10 minutes. Adjust the seasoning if necessary, then return the shanks to the sauce to rewarm briefly before serving. Serve as desired, garnished with a sprinkling of parsley.