Dip the pieces of osso buco in flour. Place the stainless steel inner pot inside the Instant Pot®. Press Saute and set time to 10 Minutes . Add the olive oil and brown meat on both sides. Set aside.
Press Saute again and set time to 10 Minutes. Add the onion and leek to the same oil and sauté for 6 minutes while stirring. Add the wine and stir for 4 minutes.
Add the meat back to the pot, salt, pepper, the crushed tomatoes and 1 cup of water.
Close and lock the Instant Pot® lid. Make sure the steam release handle is turned to Sealing. Press Pressure Cook, pressure level High, and set time to 30 Minutes.
When done, press Cancel and let the pressure release naturally for 10 minutes. Then turn the steam release handle to Venting. Once all the pressure has been released, open the lid and serve.