Steak and Parmesan Mash with Peppercorn gravy

• 3 tbsp extra virgin olive oil
• 2 scotch fillet steaks
• 4 medium potatoes, peeled and diced
• .3 cup parmesan
• .25 cup milk
• 200 g green beans
• 100 g asparagus
• .25 cup green peppercorns
• .75 cup beef stock
• 1 tsp Dijon mustard
• 1 tbsp white wine vinegar
• .5 cup milk
• 2 tsp corn flour