Lamb steaks with parsnip mash

For the parsnips:

800g parsnips, peeled and cut into small dice

80g butter

1 tbsp good quality French Dijon mustard

salt

pepper

1 tsp lemon juice

drizzle of rapeseed oil

For the lamb:

4 nice sized lamb steaks (around 180g each)

50g butter

sea salt

black pepper

1 tsp cumin

small handful of parsley or mint, chopped