Mix all the marinade ingredients together in a medium-sized bowl and whisk until thoroughly combined.
When the marinade is ready, place the steaks in the same bowl, or even a Ziplock bag, with the filet mignon marinade and allow them to soak – or marinate – for two hours.
It is recommended longer for steaks of less tenderness, but for a filet mignon, less is more.
Make sure to leave the marinade out on the kitchen counter at room temperature.
The steak needs to be neither hot nor cold when it is ready to be grilled. This is the longest part of the process, but fortunately, it also is the easiest.
When the steak is done marinating, it is time to heat up the grill. For the best result, the grill needs to be around 450 degrees but not more than 500 degrees. On most grills, this is around 75 percent. Not only do you need to know your grill temperature, you also need to know steak temperatures. This is vital in cooking the perfect grilled filet mignon.
Your steak is cooked extra-rare when it is very red and cold with a temperature of 115 to 120 degrees; rare when it has a cold red center and is soft, 125-130 degrees; medium rare when it has a warm red center and is firmer, 130-140 degrees; medium when the steak is pink and firm, 140-150 degrees; medium well when there is a small amount of pink in the center, 150-155 degrees and well-done when the steak is gray-brown throughout and firm, 160-212 degrees.
Now that your grill has reached the correct temperature and you know what temperature your steaks need to reach in order to be cooked the way you and your guests like, it is time to throw the steaks on the grill and close the lid.
Grill for six minutes, rotating halfway through. Continue flipping and grilling until your steak reaches its desired temperature.
Make sure to never, ever puncture the steak with the tongs while rotating, it can ruin the steaks texture and tenderness. Just be very careful when turning.
For example, an additional six minutes would reach 145 to 150 degrees internal temperatures.
Remove the steaks from the grill and make sure to lightly foil the steaks for an additional five minutes while the juices finish settling in the meat.