Amir Mostafavi was a D.C. pioneer when it came to cold-pressed juice, smoothies, and acai bowls. But now, regional cult-favorite fast casual South Block has its sights set on big-time growth. The brand’s 15th location will open in summer 2023 at the East Coast Amazon HQ2 in Arlington. The unit will mark South Block’s fourth opening within a 12-month period. Yet this mission-driven journey is just getting started.