OK, let's see if I have this right.
Put Olive Oil, Herbes de Provence, Mustard seed and "special mix" and let it sit for how long? This is a sort of marinade, right?
The Special Mix:
Dry coriander Seeds, right? Or Ground?
Dry onion Flakes or Onion Powder?
Dry red sweet pepper (this) We have this available as flakes or chunks
dry green sweet pepper (this) Flakes or Chunks?
Black pepper
Carum carvi seeds (a sort of cumin aka Cuminum cyminum) Here that is "Caraway seeds"; easy to get.
Mustard seed Easy to get.
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How long do you let this sit on the cote before cooking?
I understand 2 minutes per side, then cover and cook 7-10 minutes MORE per side? That's a LOT of cooking... it'd be 25 minutes! I usually have my steaks done in about 10, 5 on each side. Are you cooking these "well done" or sort of "medium rare?" How hot is the fire?