1.5 kg scotch fillet roast
6 parsnips, trimmed and chopped
12 baby carrots, trimmed
2 red onions, peeled and quartered
1 bulb of garlic, halved horizontally
6 tbs seeded mustard
½ tsp salt
½ tsp pepper
¼ cup pan juices
4 tbs corn starch
½ cup water + 1 cup water