Wash and dry all produce. Trim, then thinly slice scallions, keeping greens and whites separate. Mince or grate garlic. Core and seed poblano, then cut into 1/2-inch squares. Drain and rinse beans.

Heat a drizzle of oil in a large pan over medium-high heat. Add pork and Mexican spice, breaking up meat into pieces. Cook, stirring occasionally, until crisped at the edges and no longer pink, 4-6 minutes. Season with salt and pepper. Remove from pan and set aside.

Add a drizzle of oil, scallion whites, poblano, and garlic to same pan over medium-high heat. Cook, tossing, until lightly browned and softened, about 5 minutes. Season with salt and pepper.

Stir stock concentrate, beans, tomatoes, and 1/2 cup water into pan. Bring to a boil, then lower heat and reduce to a simmer. Let bubble until slightly thickened, about 5 minutes. Season with salt and pepper.

Return pork and any drippings to pan, stirring to combine. Simmer until saucy and very thick, about 5 minutes longer.

Divide chili between bowls. Sprinkle with cheddar and dollop with sour cream. Garnish with scallion greens and serve.