Ramp and potato soup with scallion and goat cheese muffins

1 tablespoon butter;

2 cups diced ramp bulbs;

11⁄2 pounds starchy potatoes (such as russets), peeled and cut into 1-inch pieces;

4 cups chicken stock;

1 teaspoon kosher salt, plus more to taste;

1 teaspoon ground black pepper, plus more to taste;

1⁄2 cup well-shaken buttermilk;

1⁄4 cup finely chopped fresh chives;

2 tablespoons finely chopped fresh basil;

1 tablespoon finely chopped fresh dill;

1 tablespoon green Tabasco sauce;

1⁄2 cup chopped scallions (white and tender green parts) or additional ramps, for serving;

Melt the butter in a large, heavy soup pot over medium heat. Add the ramps and cook, stirring frequently, until softened but not browned, about 8 minutes. Add the potatoes, stock, salt, and pepper and simmer gently until the potatoes are completely tender and falling apart, about 45 minutes.
Puree 2 cups of the ramp mixture in a blender and return to the pot, or puree part of the mixture directly in the pot with an immersion blender. The puree thickens the rest of the soup.
Stir in the buttermilk, chives, basil, dill, and Tabasco and warm through over low heat, about 5 minutes. Season with salt and pepper. Sprinkle the soup with scallions and serve warm with the muffins.
Variation: Nothing else in the world tastes like ramps, but if you have no access to ramps, you can still make great soup by substituting 11⁄2 cups chopped spring onions and 1⁄2 cup coarsely chopped garlic.
Make-ahead note: This soups tastes best made 1 day ahead. Cool to room temperature, cover, and refrigerate. Reheat gently over low heat.