To a large Dutch oven (or other heavy-bottomed pot) over medium heat, add 1 tablespoon oil.
Once the oil is hot and shimmering, add the diced onion. Cook, stirring occasionally, until softened, about 4 to 5 minutes.
Add the garlic, oregano, chili powder, and cumin. Stir and cook for 1 more minute.
Pour in the chicken broth and stir to combine. Bring the mixture to a gentle simmer.
While the broth is heating, add the remaining tablespoon of oil to a medium skillet over medium-high heat. Once hot and shimmering, add the frozen corn and cook, stirring occasionally, until lightly charred, about 5 minutes. Remove from heat and set aside.
Once the broth is simmering, stir in the beans, shredded chicken, and charred corn.
Meanwhile, in a small bowl, whisk together the cornstarch and cold water until smooth. Stir the cornstarch slurry into the chili. Continue to simmer, stirring occasionally, for 8 to 10 minutes, until slightly thickened.
Reduce the heat to low. Stir in the sour cream, shredded cheese, and lime juice until fully incorporated. Season to taste with salt and pepper.
Serve warm, topped with queso fresco, jalapeño, fresh cilantro, and tortilla strips, if desired.