If you are using a leftover onion ring, place it onto a baking sheet into a preheated 350 degree oven for about 7 minutes to re-crisp the onion ring.
When the onion ring is nice and crispy, remove it from the oven, and set it aside.
Heat a non-stick skillet on medium heat. Add the oil, and the butter, and give that a nice swirl. Once the oil and butter are heated through, add the onion ring to the center of the skillet.
Crack the egg, and carefully pour the egg inside of the onion ring.
Cook the egg for about four minutes, then cover, and remove from the heat. Cook an additional 2 minutes or so, until the egg white has stiffened. Uncover and season with salt and pepper.
Slide the egg onto your serving plate, and slice into it.
The end result was nothing short of amazing. In fact, as I sliced through the first bite, I kind of giggled about how awesome this thing was. It has the great texture from the crunch of the exterior of the onion ring, a sweetness from the onion, and the perfect dressing from the yolk. I impressed myself to say the least.