Place poblanos on a foil-lined baking sheet and broil on high for 10–12 minutes, turning once, until blistered and charred.
While the peppers are roasting, heat 1 tablespoon of avocado oil in a large skillet over medium heat. Add the diced onion and cook for 2–3 minutes, until softened. Stir in the minced garlic and cook for 30–60 seconds, just until fragrant. Transfer the cooked onion and garlic to a high-speed blender and set aside.
Remove the poblanos from the oven and immediately place them in a bowl. Cover the bowl with a towel and let them steam for 5 minutes.
While the peppers are steaming, add a drizzle of oil to the skillet, and season the shrimp with a little bit of salt and pepper. Add the shrimp to the skillet in a single layer and cook 2 minutes per side until pink and opaque. Remove and set aside.
Once the peppers have finished steaming, place them on a cutting board. Gently peel off the charred skins using your hands or tongs; be careful, they will still be hot. Cut off the tops, remove the seeds and membranes, and roughly chop the peppers.
Add the roasted poblanos to the blender with the onion and garlic. Pour in the milk, broth, and flour. Blend until smooth and creamy.
Pour the poblano sauce into the skillet. Add salt, pepper, cumin, and smoked paprika. Bring to a gentle simmer and cook for about 5 minutes, until slightly thickened.
Return the shrimp to the skillet and simmer for 1–2 minutes, just until fully cooked and warmed through. The shrimp should reach an internal temperature of 125–130°F.