Bring a large pot of salted water to a boil. Wash and dry produce. • Core, deseed, and dice poblano into ½-inch pieces. Trim and thinly slice scallions, separating whites from greens. Peel and thinly slice garlic. Finely chop tomato.
In a large bowl, combine a large drizzle of olive oil, Blackening Spice, and a few big pinches of salt. • Pat chicken* dry with paper towels; add to bowl and turn to coat.
Once water is boiling, add penne to pot. Cook, stirring occasionally, until al dente, 9-11 minutes. • Reserve ½ cup pasta cooking water (1 cup for 4 servings), then drain and set aside.
While pasta cooks, heat a drizzle of olive oil in a large pan over medium-high heat. Add poblano and a pinch of salt. Cook, without stirring, until lightly charred, 3-4 minutes. • Add chicken and cook, stirring occasionally, until browned and cooked through, 4-6 minutes. • Stir in scallion whites and garlic. Cook until fragrant, 1 minute. • Stir in half the tomato and a pinch of salt. Reduce heat under pan to medium low.
Stir in cream cheese and 1⁄3 cup reserved pasta cooking water (2⁄3 cup for 4 servings). • Add drained penne and cook, stirring, until thoroughly combined, 1-2 minutes. Turn off heat. • Add Monterey Jack, stock concentrate, 2 TBSP butter (3 TBSP for 4), and as much hot sauce as you like; stir until butter has melted. Season with salt and pepper. TIP: If needed, stir in more reserved cooking water a splash at a time until pasta is coated in a creamy sauce.
Divide pasta between bowls or plates. Garnish with scallion greens and remaining tomato. Drizzle with any remaining hot sauce if desired and serve.