When steaks are more than an inch thick, it's usually better not to cook them start to finish on the stove top -- grill pan or no. The restaurant style is often called "sear and blast."
Use a a good, heavy pan (stainless is fine), preferably non-stick.
Preheat the oven to 400F for at least 15 minutes. Alternatively, if you have a convection oven, preheat to 350F with the fan on.
Note the weight of your largest steak. If the steaks were not separately wrapped and weighed you'll have to estimate.
When you're ready to cook, preheat the pan over medium-high heat until you think it's hot enough, add a tiny bit of oil, swirl the pan so the oil completely covers the bottom, and continue pre-heating until the oil shimmers. Shimmer is the low end of "hot enough," and just starting to smoke is the high end.
Add the seasoned, "temped" (to room temperature) steaks to the pan, and sear them. Do not try and move the steaks, or lift them to check on their progress.
After about 90 seconds, shake the pan. If the steaks slide around, they're ready to to turn. If not, check again in 30 seconds and keep checking every 30 seconds; but do not let your steaks go longer than 3 minutes total on the first side. There are two reasons you want the steaks to "release" on their own. First you don't want to disturb the delicious crystalized juices on the outside; and second, the release point is a never-fail indication of the perfect sear.
After the steaks move (or after 3 minutes), turn the steaks. Allow them to cook for 30 seconds, no more no less. Then place the pan in the oven. The reason you only allow thirty seconds on the second side is that the pan carries residual heat and the steaks continue to sear for a couple of minutes after going into the oven.
Once the steaks are in the oven, roast for 10 minutes per pound for rare, or 12 minutes per pound for mid-rare, basing your estimated cooking time on the weight of the largest individual steak. It doesn't matter how many steaks you have in the pan, calculate your time by the largest individual steak. Don't forget to subtract the amount of time the steaks spent searing from the total time.
So, if you have two one pound steaks which took 2min 30sec to sear, and you want to cook to medium rare, you have 9min 30sec in the oven.
After roasting for two minutes less than the calculate time, "press test" the steaks. If you don't know how to press test accurately, just cook to your calculated time and hope for the best. When the steaks are done, remove them from the pan and let them rest -- preferably on a rack -- for no less than five and no more than seven minutes.
While the steak seared on the stove top and roasted in the oven, fond developed on the bottom of the pan. It would be a sin to waste it, use it for a pan sauce.