Gather all of your ingredients.
Prepare your veggies.
Peel the potatoes and chop them into cubes.
Clean the mushrooms by wiping them with a damp paper towel. If you wash them, they get soggy - so don't do that.
Discard the mushroom stems and thickly slice the caps.
Dice the onion.
Put the 4 cups of broth into a stock pot. Add the potatoes and bring to a boil. You will cook them for about 12 minutes until they can be pierced with a fork, but are not falling apart. If they get soft and the other steps are not ready, just lower the heat.
While the potatoes are boiling, melt the butter in a frying pan.
Add the onions and mushrooms to the melted butter. Sprinkle with paprika and cook until soft, about five minutes. Don't let the pan get too dry. I had to add more a little more butter. Stir regularly.
While everything else is cooking, prepare your roux by combining the milk, heavy cream, and flour. I did that in a measuring cup and mixed it with a fork.
When the mushrooms are ready, add the roux. NOTE: I had a bit of excess liquid in my pan, so I poured it off first. Stir regularly and heat through until thickened, about three minutes.
Add the creamy mushroom mix to the potatoes and broth.
Stir in the fresh thyme.
Stir in the sour cream.
Let cook until the entire thing is heated through.