Press Saute on the Instant Pot and while it’s heating, cut a clove of garlic in half and rub it all over the lamb. Season it with salt and pepper. Slice or chop the garlic cloves and the herbs. When the IP display says Hot, add the oil and the lamb, fat side down.
Brown it well and then transfer it to a plate and press Cancel. Pour the broth and wine, if using, into the pot. Deglaze the pot: stir any brown bits up off the bottom. Add the garlic and herbs and put the lamb back in, ribs side down. The rib bones will act as a trivet of sorts.
Close the pot, set the valve to Sealing and hit Pressure Cook (or Manual). Use the +/- buttons to get to one minute. One. This will produce medium-rare meat.
When it beeps that it’s done, leave it for a 12-minute natural release. Then hit Cancel and flip the valve to Venting to release the remaining pressure. When the pin drops, open the pot, transfer the lamb to a plate and tent it with foil. Let the lamb rest for 5-10 minutes while you make the sauce.
Press Saute and bring the broth to a boil. Let it reduce to about 1/2 cup. Add the butter cubes one at a time, whisking vigorously to emulsify the sauce. Taste and adjust seasoning with salt and pepper if needed.
Carve the lamb into chops and plate with a drizzle of the sauce over each serving.
Pressure Cook and Manual buttons are interchangeable.