In a large saucepan over medium heat, melt the butter. Add the diced onion and poblanos and sauté until softened, about 5 minutes.
3 tablespoons butter, 1 onion, 3 large poblanos
Sprinkle in the flour and whisk constantly for 1 minute to cook out the raw taste.
3 tablespoons all-purpose flour
Stir in the minced garlic and cook for another 30 seconds.
3 cloves garlic
Slowly pour in the seafood stock while whisking to prevent lumps.
2 cups seafood stock
Simmer for 2 to 3 minutes until the sauce thickens slightly. Reduce the heat and stir in the sour cream.
1 cup sour cream
Simmer gently for another 2 to 3 minutes until thickened and creamy.
Remove from heat and stir in the salt, pepper, 1 cup of shredded cheese, and chopped cilantro.
2 cups Monterey Jack cheese, 3 tablespoons chopped cilantro
Set aside.