Heat oven to 400ºF. In a medium bowl, whisk together the olive oil and 1 teaspoon miso paste. Add the chickpeas and mix to coat. Spread on a baking sheet in a single layer. Bake 30 minutes, stirring halfway through.

In a large soup pot, melt the butter over low heat. Add the onions and cook until softened, about 5 minutes. Stir in the garlic; cook 1 minute. Stir in the miso paste.

Add the potatoes to the pot and pour in enough stock to cover the potatoes. Increase heat to medium-high and bring to a simmer. Let simmer until the potatoes are just fork tender, 10-15 minutes.

Transfer half of the soup to a blender; blend until smooth. Repeat with remaining soup.

Serve topped with scallions and crispy chickpeas.