Cut off the dark green stem and the root off the leek (save the green parts to use in homemade broth). Cut the white and light green parts only of the leek lengthwise down the middle, then cut into ½ inch half moons slices. Place leek pieces in a large bowl of water and separate the pieces with your hands to clean the dirt off. Lift the cleaned pieces out of the dirty water and set aside. Throw out the dirty water.
Turn on the saute button on the Instant Pot and add the bacon. Cook for a few minutes, until lightly browned and oil is released. Remove the bacon and set aside.
Add the leek and onion to the bacon grease in the pot and saute for 3-5 minutes, until veggies are wilted. Turn off saute option and add the carrots, potatoes, broth, and marjoram to the Instant Pot. Cover with the Instant Pot lid; making sure it's locked and the steam value is in the closed position. Select the manual 15 minutes high pressure.
When the soup is finished cooking, wait 10 minutes for the Instant Pot to cool down or release pressure manually by taking a hand towel and carefully opening up the steam value on the lid. It is safe to open the lid once all steam has been released.
Using an immersion blender, puree the soup until smooth. Add salt and pepper to taste and stir in the sliced wieners to heat through. Serve in large bowls and a sprinkling of garlic chives, if desired.
Leftovers can be stored in a tightly covered container in the refrigerator.
Soup can be frozen for up to 3 months. Thaw in the refrigerator and blend the soup again before heating to get a smoother consistently.