I'm not getting what you mean by a crunchy crust. If you want a crust like fried chicken, you're going to end up breading and frying the steak. If you want a steak like you'd get by grilling it in a pan or on a "barbeque grill" -- not that you can't develop some good texture with a dry rub and a sear -- you're not going to get anything very crunchy or particularly crusty. But language can be trickier than cooking techniques. Sometimes the crystalized sugars on meat which has been seared or otherwise browned is referred to as a "crust." Hence my confusion as to your meaning.
If you're willing to cook something more like chicken fried steak (which is going to have a crust like... wait for it... fried chicken), that's pretty easy. Start with a relatively thin steak, and tenderize it by pounding or using a jaccard. Simply crush the corn or potato chips of your choice, and use them for a breading, You can either use a three-pan breading of flour - egg - crushed chips; or a one pan breading of the crushed chips, perhaps mixed with some ordinary flour. Then fry the steak in fairly hot oil that's about 1/3 of the steaks' height.
On the other hand, you might want to consider "blackened" steak which will not only give you a lot of texture but allow you to cook "black and blue," without the intense heat of a professional broiler or a grill with a fresh, live fire.
To blacken a steak, coat it very well with the spice rub of your choice -- you'll want to use a lot of chili (probably chili de arbol), salt and garlic in yours, or you could use any spicy, cajun blakening rub and increase the amount of chili -- rub the rub into the steak, and allow the steak to sit for at least 30 minutes. Meanwhile, heat a cast iron skillet until it's very, very hot. Sear the steak on both sides until it's completely black on the exterior. If the steak needs further cooking to reach your desired degree of doneness (blackened steak is usually cooked no more than mid-rare), finish it in the oven on a baking sheet or a fresh pan. Note: If you keep the steak in the cast iron pan you used for the initial sear, the down side will become tough as leather.
Breading and frying ala chicken frying is the only way to get real crunch. Blackening is the next, best bet.