Wash and cut the asparagus, discarding the ends that are tough and stringy. Set aside.

Turn on the Sauté setting. When hot, add the butter and the onion. Cook for a few minutes, stirring occasionally.

Add the asparagus. Cook, stirring occasionally, until softened.

Add the broth and salt.

Turn off the sauté setting.

Close the lid and set the steam release knob to the Sealing position.

Press the Pressure Cook/Manual button or dial, then the +/- button or dial to select 7 minutes. High Pressure. The pot will take several minutes to come to pressure.

When the cook cycle has finished, turn off the pot and let it sit undisturbed for 10 minutes (10 minute natural release). Then turn the steam release knob to the Venting position to release the remaining steam/pressure.

When the pin in the lid drops back down, open the lid.

Use an immersion blender to puree the hot soup.

Add 1 cup of the milk.

Turn the sauté setting back on.

Whisk together the remaining ½ cup of milk with the flour to make a slurry. When the soup starts to simmer, whisk in the slurry.

Turn off the pot.

Ladle out a little of the soup and mix with the sour cream to temper it. Then stir it into the soup.

Stir in the lemon juice.

Taste and adjust salt if needed.

Serve hot or chilled. Garnish with fresh cracked pepper.