In a non-stick frying pan over medium-high heat, sauté onion and garlic until onion softens, about 3 minutes. Add ground cumin, ground coriander, and cayenne pepper (omit for kids) and stir for 1 minute.
Brown the mince, breaking up any lumps with a wooden spoon, until it changes color, about 5 minutes. Add diced tomato, tomato paste, and kidney beans. Simmer over medium heat for 10 minutes, stirring occasionally, until the mixture thickens. Remove from heat, add chili (optional), and season with salt and pepper to taste.
In a small bowl, mix together the sour cream, most of the green shallots, and coriander leaves. Season with salt and pepper to taste.
Heat tortillas according to package instructions. Fill bowls with chili con carne. Add a dollop of the sour cream mixture on top. Finish by sprinkling with the remaining green shallots. Serve promptly.