Smoky Vegetarian Potato Soup

Heat 1 tablespoon butter and olive oil in a stockpot over medium-low heat. Add onion and cook until browned, about 3 minutes. Add garlic salt, tarragon, and liquid smoke; cook until onion is translucent, 2 to 4 minutes more. Add potatoes and vegetable stock; bring to a boil. Boil until potatoes are tender and stock has been reduced to about 1 cup, 15 to 20 minutes.

Meanwhile, melt remaining 1 tablespoon butter in a skillet over medium heat. Stir in cornstarch and mix completely, being careful not to burn. Add half-and-half and cook until thickened, 3 to 5 minutes. Add to potato mixture and heat through, 2 to 3 minutes. Garnish with Cheddar cheese and parsley.