• Wash and dry produce.

• Trim and thinly slice scallions, separating whites from greens. Dice tomato into 1/2-inch pieces. Quarter lime.

• Pat chicken dry with paper towels. Cut into 1-inch cubes.

• Heat a drizzle of oil in a medium pot over medium-high heat. Add scallion whites, chicken, salt, and pepper. Cook, stirring occasionally, until scallion whites are tender and chicken is warmed through, 2-4 minutes.

• Add tomato, Tex-Mex paste, and stock concentrates; stir to combine. Stir in 21/2 cups water (4 cups for 4 servings); bring to a simmer, then reduce heat to medium low. Cook, stirring often, until flavors meld and soup has thickened slightly, 4-6 minutes. Taste and season with salt and pepper. Remove from heat and stir in half the sour cream.

• Divide soup between bowls. Dollop with remaining sour cream and sprinkle with scallion greens. Crush tortilla chips over top and serve with a squeeze of lime juice.