Chop the parsley, garlic and basil into small pieces. Cut the broccoli and spring onions into small pieces. Chop the tomatoes if necessary.
Put a large saucepan of salted water on the boil. Put the tagliatelle in the pot and shortly afterwards add the broccoli to the boil.
Gently heat the butter, the white of the spring onions, garlic, parsley, basil and mustard in a heat-proof bowl on the stove until the butter has melted and the herbs and garlic release their aromas. Take it off the stove.
Pour off the water from the pasta and pour in the mustard sauce, spring onions and tomatoes and mix everything well.