Steak with Classic Mushroom Sauce

Ingredients

• 600g frozen rosemary and garlic roast potatoes
• 50g unsalted butter, chopped
• 1/4 cup extra virgin olive oil
• 1 brown onion, halved, finely chopped
• 200g Swiss brown mushrooms, sliced
• 200g white cup mushrooms, sliced
• 2 tbs plain flour
• 1 1/3 cups salt-reduced beef stock
• 1 tbs Worcestershire sauce
• 2/3 cup thickened cream
• 1 tbs Dijon mustard
• 4 sprigs thyme, leaves picked
• 6 beef scotch fillet steaks
• 2 bunches broccolini, steamed