Preheat the oven to 400 degrees F. Butter a 9-by-13-inch glass or ceramic baking dish.
Heat a medium Dutch oven over medium heat. Add the butter, and once it melts, add the beef and sprinkle with 1 teaspoon salt. Cook, crumbling with a wooden spoon, until browned, 4 to 5 minutes. Add the bell pepper and scallions (saving a handful of the greens for garnish) and cook until the vegetables begin to wilt, 2 to 3 minutes. Add the paprika and several grinds of pepper, then stir to coat the beef in the spices. Stir in the corn.
Sprinkle the flour over the beef and stir to incorporate. Cook and stir until the flour begins to toast, about 2 minutes. Add the broth and cream gradually while stirring. Bring to a simmer and cook until the sauce thickens, 3 to 4 minutes. Stir in the parsley, mustard, dill and thyme. Pour the mixture into the prepared baking dish. Arrange the curly fries in a tight layer over the top. Sprinkle with the cheese. Bake until the cheese and fries are crispy and the sauce is bubbly, about 40 minutes. Sprinkle with the reserved scallion greens and serve hot.