Grill corn and poblano chiles for flavor

Transfer chiles to a bowl, cover immediately with plastic wrap, and let steam 15 minutes. Peel and discard charred skin from chiles, and remove stems and seeds. 

Halve chiles lengthwise, and slice crosswise into 1/4-inch-thick strips.

Add corn, the salt, and 2 cups stock to blender. Puree until smooth, about 1 minute. 

Transfer puree to skillet along with butter and milk. Cook for 5 minutes constantly stirring Stir in remaining stock . 

Bring to a boil over high heat, reduce heat, and simmer, stirring occasionally, until thickened slightly, about 15 minutes. 

Pour in bowl and emulsify with immersion blender then pass through sieve. 

Divide soup among 6 bowls; garnish with chopped scallion greens, and sprinkle with cheese. 

Soup can be refrigerated 2 days; let cool completely before refrigerating. Gently reheat in a covered pot over medium heat, stirring occasionally, or serve chilled.