Prepare The Spice Mix
Combine the coriander, cumin, turmeric, cinnamon, mustard powder and chilli flakes. Heat a dry pan over a medium heat and add the spice mix. Dry fry, tossing every so often, until you can really smell the toasting spices.
Dice the beef into large pieces and tip half of the spice mix over it.
Pour over the 1 tbsp of vegetable oil and coat the beef completely. Marinate for a few hours, or overnight.