Bring a large pot of water to a boil. Salt generously, then add the pasta. Cook until al dente. Before draining, reserve about 1 cup of the pasta water, then drain the pasta and set aside.

While the pasta is cooking, chop the poblano pepper and the onion. Mince the garlic.

Melt 4 tablespoons of the butter in a large skillet. Add the pepper and onion and cook until they are starting to soften, about 7 to 8 minutes. Add the garlic and cook an additional minute.

Sprinkle the flour over and stir to combine. Let this cook for another minute or two. Slowly whisk in the chicken broth. Let the mixture simmer for about 5 minutes, or until it has slightly thickened.

While the sauce is thickening, warm the crema. You can do this in a small pot on the stove or in the microwave. Once the sauce is slightly thickened, turn off the heat and stir in the warmed crema. Transfer the mixture to a blender or food processor and process until smooth.

Wipe the skillet out and add the remaining 2 tablespoons of butter. When melted, add the shrimp and cook until the shrimp are pink. This will only take a couple of minutes. Pour the poblano sauce over the shrimp and stir to combine.

Add the pasta and stir to combine. (I think this is easiest to combine everything in the pasta pot - it’s bigger and easier to stir everything together without making a mess.) If needed, add some of the reserved pasta water to loosen the sauce. Season to taste with salt and pepper.