Pop the venison steaks into a dish. Measure out 1 tsp mustard and place it in a small bowl. Peel and grate the shallot into the bowl with the mustard. Add 1 tsp olive oil and a pinch of salt and pepper. Stir to mix together. Rub the shallot and mustard marinade into the steaks. Set aside.
Tip the barley into a sieve and give it a rinse. Tip it into a medium pan. Pour in enough boiling water to cover the barley by 5cm. Add a pinch of salt. Cover, bring to the boil, then turn the heat down and let the barley simmer for 15 mins till the grains are almost tender.
While the barley simmers, peel and grate or crush the garlic. Finely chop the parsley leaves.
Pop the garlic in a small bowl with the parsley and 1 tbsp balsamic. Add 2 tsp olive oil and some salt and pepper. Whisk together, taste and add more salt and pepper if it needs it.
Put a griddle pan on a high heat to warm up. When it's smoking hot, add the venison steaks. Cook for 3-5 mins on each side, depending on how well done you like your steaks. Pop them on a plate and loosely cover with foil. Let them rest for 5 mins.
Break the broccoli up into small florets. When the barley has cooked for 15 mins, add the broccoli to the pan. Simmer, without the lid on, for 5 mins till the broccoli is just cooked and the barley is tender.
Drain the barley and broccoli and tip it back into the pan. Add the balsamic dressing and toss to mix. Serve the venison steaks with the warm barley and broccoli salad and the remaining mustard on the side.