Heat a large drizzle of oil in a large pan over medium-high heat. Add beef, chili powder, scallion whites, remaining Southwest Spice, salt, and pepper. Cook, breaking meat up into pieces, until browned and cooked through, 6-8 minutes. Drain off any excess oil from pan. Add stock concentrates, ⅓ cup water, and 2 TBSP butter. Stir until thoroughly combined and butter has melted.