Heat olive oil in a medium saucepan over medium heat. Add onion and poblano pepper and cook 4-5 minutes or until onions are translucent. Add garlic and corn and continue cooking for an additional 3 minutes. Season with salt and pepper.
Pour milk and broth into the saucepan and bring to a boil over high heat. Stir in grits and reduce heat to low. Cook for 40-45 minutes stirring frequently or until grits are thick. If grits absorb all the liquid before they are done, add additional hot chicken broth or water as needed.
Remove from heat and stir in butter and cheddar cheese. Season with salt and pepper.
Garnish with cilantro and scallions and serve immediately.