Preheat Grill. Prepare grill for direct heat targeting 400 degrees Fahrenheit in the cooking chamber. As the grill warms up, place a cast iron pan (or other grill safe pan) in the grill to warm up as well.
Season. Combine rub ingredients in a small bowl. Place sirloin cubes in a large bowl and cover with olive oil and the rub. Mix together with your hands.
Grill Sirloin. Add olive oil to the hot pan and then add the seasoned steak pieces. It will sizzle quickly, be sure to move the steak around so it’s all touching the pan. Close the lid and let the steak bites grill for 3 minutes. After 3 minutes, start moving the bites around in the pan with tongs. Continue grilling another 3 minutes. Take the temperature of a few of the steak pieces using a good quality instant read thermometer. It should ready close to 125, if it’s under 125 then keep turning until they reach the range of 125 – 130 degrees Fahrenheit. Then remove steak and place into the clean bowl.
Make Pan Sauce. Add butter and shallots to the pan and stir while the pan remains on the grill. This will start the deglaze process. After 3 – 4 minutes, when shallots are soft, add the garlic and stir for 1 minute. Add the wine and balsamic vinegar and continue to stir until all the flavor bits in the pan are scraped off and the sauce is incorporated. About 2 minutes.
Return Steak to Pan. Add the steak bites back into the pan, toss together and then place them in a serving bowl.
Stovetop: You can make this on the stovetop as well. Simply repeat steps over medium-high heat on the burner. Adjust heat down if it's too hot.Variation: If you like sweeter style sauce, you can sub the pan sauce for your favorite BBQ sauce. Simply remove the steak bites and pan from heat. Then add 1 cup of BBQ sauce, stir to combine with bits in the pan and toss back the steak bites. Try our Kansas City Style Sauce if you want to make your own.