Melt butter in a Dutch oven over medium heat. Add onion and jalapeño, and cook 10 minutes, stirring frequently. Add curry, and cook 30 seconds, stirring constantly. Add stock and corn, and bring to a boil, stirring occasionally. Reduce heat; simmer 15 minutes.
Lightly spoon flour into a dry measuring cup, and level with a knife. Place flour in a small bowl; gradually add milk, stirring with a whisk until well blended to form a slurry. Stir slurry into corn mixture, and bring to a boil. Cook for 3 minutes or until mixture thickens, stirring frequently. Stir in chicken, cilantro, salt, and black pepper.