Recently I've become a fan of French cook and food writer Sonia Ezgulian. Her little book 'Petits Ricochets de Cuisine' focuses on ideas for getting the most out of a dish or set of ingredients, by getting more than one meal from every cooking session. She deliberately cooks with leftovers in mind.
Shred the cooked meat, then mix with a ladleful of cooking liquor. Don't strain out the pieces of mushrooms and carrot because they give flavour and colour to the terrine. Heat up some fortified wine like muscat-de-rivesaltes or banyuls and dissolve some softened gelatine in it. Add it to the meat mixture.
Make a hash of parsley, garlic and anchovies in olive oil. Line a terrine with clingfilm and put in half the beef mixture, followed by the persillade, topped off with the rest of the beef. Press it lightly and put in the refrigerator for a few hours to set.