Green Dragon Steak
Thaw the flat iron and remove the package. Trim any excess fat or silver skin. Season with kosher salt and fresh cracked pepper on both sides.
Heat oven to 350 °
Heat cast iron skillet over medium-high heat. Add a tablespoon of grapeseed oil and allow to heat.
Sear flat iron on each side for 3 to 4 minutes, setting up a nice golden brown crust.
Place skillet and steak in oven. We want to get the internal temp to 130°, so you'll need a good digital thermometer like a Thermapen. The total time will be about 10 minutes. At 5 minutes flip steak over.
When the internal temp is 130°, pull the steak from the oven. Put on a cutting board and loosely wrap with foil.
Let rest for 15 minutes.
Slice the steak against the grain and arrange on a platter. Top with sauce. Sprinkle green onions and toasted sesame seeds. Serve extra sauce on the side, if you desire.
Sauce
Place all ingredients in a saucepan over medium heat. Stir until sugar melts and sauce bubbles gently. Simmer for 10 minuts. Remove from heat.
Strain the sauce. Set aside until time to use. This can be made in advance. Keeps for a week or more in the refrigerator.