Stroganoff on Rice

1. Sear the steak hard on both sides for colour, then set aside almost raw in the middle.
2. Cook diced onion in butter until soft. Add mushrooms and cook until just softened — don't let them shrink to nothing.
3. Sprinkle flour over the buttery mix and stir for a minute so it cooks out.
4. Add stock cautiously at first, stirring out any lumps, then pour in the rest.
5. Add sour cream and mustard. Bring to just below a boil, then simmer until thickened.
6. Slice the rested steak into thin strips. Stir in right before serving — it finishes cooking in 1–2 minutes and stays tender.
7. Serve over rice.