Bring a large pot of salted water to a boil.

Heat a large dry pan over medium-high heat. Add bacon*; cook, turning occasionally and reducing heat if browning too quickly, until crispy, 6-10 minutes. Turn off heat; transfer to a paper-towel-lined plate. Carefully discard all but a thin layer of bacon fat from pan.

Once bacon is cool enough to handle, roughly chop.

Wash and dry produce.

Trim and thinly slice scallions, separating whites from greens. Peel and mince or grate garlic.

Once water is boiling, add spaghetti to pot. Cook, stirring occasionally, until al dente, 9-11 minutes; drain.

While pasta cooks, pat chicken* dry with paper towels; place between two large pieces of plastic wrap. Pound with a mallet or rolling pin until chicken is about ½ inch thick. Season with salt and pepper; dust all over with flour, shaking off excess.

Heat pan with bacon fat over medium-high heat (if there’s not enough bacon fat, add a drizzle of oil). Add chicken; cook until browned and cooked through, 4-6 minutes per side. Turn off heat; transfer to a cutting board. Wipe out pan and let cool slightly, 1-2 minutes.

Heat a drizzle of oil in same pan over medium heat. Add scallion whites and garlic; cook, stirring constantly, until fragrant, 30-60 seconds.

Add miso sauce concentrates, pork ramen stock concentrate, half the Sriracha, ½ cup cold water, and a pinch of sugar (all the Sriracha and ¾ cup cold water for 4 servings); bring to a simmer. Add spinach, drained spaghetti, and bacon; toss until pasta is evenly coated and spinach has wilted. TIP: Add water 1 TBSP at a time if sauce is too thick.

Turn off heat and stir in sour cream and 2 TBSP butter (4 TBSP for 4). Taste and season with salt and pepper if desired.

Slice chicken crosswise.

Divide pasta between shallow bowls; top with Parmesan, chicken, and scallion greens. Serve.