Veggies, grains, herbs, spices—this chili's got it ALL.
In a large pot or Dutch oven, heat the oil over medium. Add the white and light-green scallion parts, the bell pepper, and garlic. Cook, stirring often, until the vegetables start to soften, about 5 minutes. Stir in the squash, stock, beans, tomatoes with juices, bulgur, chili powder, and chipotle pepper. Reduce heat to medium-low. Cover and simmer, stirring occasionally, until the squash and bulgur are tender, 25 to 30 minutes.
Divide the chili among bowls. Garnish with sour cream and the dark-green scallion parts.