On medium high heat in a large thick-bottom stock pot, cook 16 ounces bacon until crispy. Remove from pot with a slotted spoon and set aside.
Keeping the heat on medium, saute 1 yellow onion, 2 celery stalks and 16 ounces mushrooms in the bacon grease, stirring occasionally until tender.
Add 3 garlic cloves, ½ teaspoon red pepper flakes and ½ teaspoon dried basil. Add 2 tablespoons arrowroot starch and quickly stir to coat vegetables with the flour. The flour should slightly cook.
Add about 1 cup of broth and stir well to create a thick consistency, making sure to lift up anything stuck to the bottom of the pot. Pour in the remaining of 2 quarts bone broth. Add diced 4 large russet potatoes. Bring to a boil, reduce heat, and simmer until the potatoes are fully cooked.
In a small bowl, temper the 1 cup Greek yogurt with 1 cup of the hot broth. Whisk to combine. Use an immersion blender to pulse just a portion of the soup to help create a smoother texture.
Transfer the tempered Greek yogurt and the bacon back to the pot and stir to combine. Bring to a gentle simmer but do not boil. Season with additional salt and pepper to taste. Top with parsley for garnish and serve immediately.
Notes
Storage: Store leftover chowder in an airtight container in the refrigerator for up to 4 days. I don't recommend freezing this soup because the dairy does not thaw well. Reheat gently on the stoveop over medium-low heat, stirring often. Add a splash of broth to loosen if needed. Avoid bringing it to a rapid boil, especially with dairy. Low and slow is the key to keeping it smooth and creamy. Helpful Tips:
Cut everything proportionally. I like to finely dice the mirepoix (onions, carrots, and celery) and keep mushrooms, potatoes, and bacon larger to get a nice bite.
Too much bacon grease? If your bacon renders more fat than you'd like, feel free to drain off a bit before adding the veggies. You want just enough left in the pot to saute everything and soak up that smoky flavor without making the soup overly greasy.
Saute mushrooms until golden. Let the mushrooms really cook down and caramelize a bit in the bacon fat. This builds flavor and prevents a soggy texture. I like to saute until I see some brown on them.
Blend just a bit for creaminess. A quick pulse with an immersion blender gives the soup a velvety texture - but don't go wild. You still want to keep those chunky bites of potato and mushroom for that cozy, rustic feel.
Troubleshooting Tips:Yogurt curdled? To prevent the Greek yogurt from curdling when added to the hot soup, make sure the heat is low and temper it first. That means stirring a ladle of hot broth into the yogurt to warm it up gradually - then stir it all back into the soup. This helps everything blend smoothly without separating. Soup too thick or too thin? If the chowder thickens more than you like as it sits, just add a splash of warm broth to loosen it up. On the flip side, if it feels a little runny, let it simmer uncovered for a few more minutes or mash a few potato cubes to thicken naturally.
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