Prep and make your fries. Scrub and wash your potatoes and slice them into your desired shapes, I like mine in between a shoestring and smaller than a wedge.
Place your cut potatoes in a bowl with ice water. This helps gets out the starch and helps get it crispy. Soak for about 30 minutes and up to 2 hours.
Place your potatoes on paper towels and pat dry completely. Heat a deep-fryer, or a deep cast iron and fill it with peanut oil or vegetable oil (any neutral oil will do) to about 300°F, about 5-6 minutes. While it's heating up, line a baking sheet with paper towels.
First fry. Add in your fries with a slotted spoon in batches for your first fry into the hot oil. You don't wan't color on the fries, just for them to be tender inside, about 10 minutes. Then transfer to your baking sheet and transfer to the refrigerator for 30 minutes and up to 1 hour.
At this point, take out your steaks to room temperature. Season with salt and pepper. *TIP: I find the fries really get crispy this way, but you can eliminate both the wait time for soaking, and wait for in the fridge after the first fry if you prefer, it will still be delicious. :)
Second fry. When it's time for your second fry, heat up that same oil to about 400°F, and take your cold fries (from the fridge) and this time you are going to brown them and make them super crispy, in batches being sure not to overcrowd the pan. Once your desired crispness, place on new paper towels on the parchment sheet to shake off any excess oil.
Transfer to a mixing bowl and toss with salt, pepper, a drizzle of olive oil, chopped parsley and parmesan, toss and set to the side.
Sear steak. Now, it's time to make our steak. Take your steak and heat a cast iron skillet until piping hot. Add in your steaks and sear on medium high heat for about 4-5 minutes to get a nice char. This will vary depending on your size of steak, though. Then flip.
Once flipped, add in your butter, rosemary and garlic cloves. Baste your steak until fully cooked to your liking (I like medium rare which is around 135°F). Let rest for about 10-13 minutes and slice against the grain.
Serve! Transfer your sliced steak to a plate and finish off with your french fries and Horseradish Cream Sauce.