Heat a large, deep frying pan over medium-high heat and fry the chorizo until crisp, about 5 minutes, stirring often. Remove onto a plate with a slotted spoon.
Add the chicken to the pan and fry for about 5 minutes, until browned all over. Then add it to the chorizo.
Add the onion and red pepper to the pan, and cook over a medium-low heat for 10-15 minutes, until the onions and peppers have softened. Add the garlic, paprika and cayenne pepper for the final minute of cooking.
Add the chicken and chorizo back into the pan with the tomatoes and chicken stock. Crush the tomatoes with a fork to break them up a little and season the paprikash lightly. Bring to a boil, then simmer for 15-20 minutes, until the sauce has reduced.
In a small bowl, combine the flour and 10g of butter into a paste. Stir this into the sauce, and simmer for 1-2 minutes, until the sauce has thickened. Stir in the soured cream if using. Scatter over the parsley.
While the chicken is simmering, cook the macaroni according to the pack instructions. Drain well, then add it back to the pan with the remaining 10g of butter, and stir, until the butter has melted.
Serve the chicken paprikash with the buttered macaroni and a lemon wedge (optional).