Turn on the Instant Pot on saute mode. Melt butter. Add Garlic, bay leaf and onions. Saute them for about a minute.
Now add carrots, broccoli and vegetable stock. Mix. Cover the instant pot, vent valve on the sealing position.
Press the manual/pressure button and set it for 3 minutes under high pressure. Let the pressure release naturally and then quick release the remaining pressure.
Heat butter in a pan. Add flour and cook it for a minute, stirring constantly.
Now add half and half, whisk constantly and cook for about 2 to 3 minutes. Make sure the mixture is lump-free.