Start by placing a heavy 9” cast iron skillet over medium heat, just a little more than medium on my electric stove.
Now pour enough peanut oil into the skillet to cover the bottom, and add the unsalted sweet cream butter. Keep an eye on it as you let it heat up. You’ll want the oil to become shimmery on the surface but not smoking.
While the oil is heating, cut the Idaho Russet or Red potatoes into even pieces—chips or cubes, whichever you prefer. As you're cutting, place the pieces into a bowl filled with 4 cups of salted water (2 Tbs of salt mixed in).
Next, take your sweet onion and cut it into larger chunks than the potatoes.
After about 5 minutes, drain the potatoes thoroughly and dry them well with paper towels. This step is crucial! If you don’t dry them properly, the oil could flare up when you add the potatoes, which can be quite dangerous.
Once your oil is ready (check for that shimmery look), carefully add the potatoes and onions into the skillet. Make sure not to overcrowd the pan; if there isn’t enough room for them to lay side by side, cook in batches.
Cook for about 4 minutes without touching them too much on one side, allowing that golden crust to form. After 4 minutes, flip the potatoes gently and cook for another 2 to 4 minutes on the other side.
Once they’re beautifully golden brown and crispy, drain the potatoes and onions on a paper towel. Immediately season with salt and pepper while they’re still hot to ensure the seasoning sticks.
For an extra special touch, garnish with a sprinkle of paprika and some fresh basil before serving hot.