1 ½poundsYukon gold potatoespeeled and cut into 1 1/2-inch chunks, about 5 medium (you can also swap russet potatoes, though I find the flavor and texture of Yukon golds more buttery)
1small head of cauliflowerchopped into florets, about 4 cups
2teaspoonsspicy brown mustard
½teaspoonground black pepper
1cup2% plain Greek yogurtor a 7-ounce container, plus additional for serving
1/2cupshredded sharp cheddar cheeseplus additional for serving
1/4cupgrated Parmesan cheese
Chopped fresh chivesfor serving
Croutonsbaguette, additional cheese, additional Greek yogurt (optional, for serving)
Turn the Instant Pot to sauté. Add the butter and let melt, then add the onion. Cook until the onion softens and turns translucent, about 5 minutes. Add the garlic and cook 30 additional seconds, just until fragrant.
Add the water to the Instant Pot. Let come to a simmer (this will take several minutes), then whisk in the bouillon. Continue to stir until it is smoothly dissolved.
Add the potatoes, cauliflower, mustard, thyme, and pepper. Cover and seal the Instant Pot. Cook on manual (high) pressure for 10 minutes. When the cooking time is up, immediately vent to release any remaining pressure.
Carefully open the lid. With an immersion blender, purée the soup until smooth, or puree the soup in batches in a regular blender (be careful not to fill the blender more than halfway. Hot soup will splatter). Return any soup you pureed in the blender to the pot. Let the soup cool a few minutes, then stir in the Greek yogurt, cheddar, and Parmesan.
Taste and adjust the seasoning as you like. Serve hot, topped with chives, additional cheese, and a dollop of Greek yogurt as desired.
TO STORE: Place cooked and cooled soup in an airtight storage container in the refrigerator for up to 4 days.
TO REHEAT: Gently rewarm soup in a Dutch oven over medium-low heat on the stove, or you can reheat your soup in a microwave-safe bowl in the microwave until warmed through. I recommend reheating your Instant Pot potato soup with milk splashes to think the soup as needed.
TO FREEZE: Store cooked and cooled leftovers in an airtight freezer-safe container or zip top bag (lay flat) for up to 3 months. Thaw overnight in the refrigerator before reheating.