Season the chicken with 2 tablespoons of the sweet and 1 teaspoon of the hot paprika, and 1 teaspoon salt.
Melt the butter in a large saute pan over medium-high heat. Add the onions and remaining tablespoon of sweet paprika, 1 teaspoon of hot paprika, and 1/2 teaspoon of salt, and cook, stirring, for 2 minutes. Add the garlic and cook for 30 seconds. Add the chicken and cook, stirring, until golden, about 4 minutes. Add the tomatoes and cook for 1 minute. Add enough stock to cover the chicken and bring to a boil. Lower the heat, cover, and simmer until the chicken is tender and cooked through, about 25 minutes, adding more stock as needed.
Uncover and add the sour cream. Cook gently until incorporated and warmed through, about 2 minutes. Season, to taste.
To serve, divide the spaetzle among 4 large plates, spoon the chicken and sauce over the noodles, and serve immediately.
Yield: 4 servings