Fill inner pot to just under maximum level with hot water.
Select sous vide mode, custom 87°C, bring up to temperature.
Have 3 sous vide compatible zipper type bags ready to fill.
Add baby potatoes, baby carrots, shallots, 20g of the butter, salt and pepper to the first bag.
Remove as much of the air as you can by lowering the bag into a bowl of water, using the water to push the air out of the bag, being careful not to allow any water into the bag. Seal while immersed or use a vacuum sealer.
When the Instant Pot has come to temperature, place the bag of vegetables in the pot, close the lid making sure the valve is open, cook for 1 hour.
In the meantime, season 2 x steaks well on both sides with salt and freshly ground black pepper.
Transfer steaks to the second bag, arrange them side by side, along with the crushed garlic cloves, rosemary and thyme. Set to one side.
In the third bag, add the asparagus spears, the remaining 10g butter, plus more salt and pepper to taste.
As before, remove as much of the air from the bags as you can. Seal and set to one side at room temperature.
After the vegetables have been in the water bath for 1 hour, reduce the temperature to 154 °C by replacing some of the hot water with cold. Check with a thermometer.
Add the steaks, asparagus, and with the vegetables still in the pot, cook for another hour.
Remove the steaks from the bag, pat dry with kitchen towel.
In heat safe place on a wire rack, using a kitchen blowtorch to sear the steaks until golden brown, or apply a little high smoke point cooking oil to them, then sear quickly (to avoid cooking through) on both sides and edges, in a very hot preheated, preferably heavy gauge pan.
Serve alongside the buttered sous vide vegetables.