Place potatoes in a large pot, cover with cold water, and season generously with salt. Bring to a boil and cook until knife tender, 20-25 minutes. Drain and return to pot to dry. Once cool enough to handle, slice into 1/2 inch planks.
Heat 2 tablespoons oil in a large cast iron skillet over medium heat. Add shallot and cook, stirring, until golden, about 5 minutes; season with salt. Remove with a slotted spoon.
Add remaining 2 tablespoons oil and potatoes to the skillet. Increase heat to medium high, and sauté until golden, 5-10 more minutes (if your potatoes are crammed in the skillet, work in batches so that all potatoes can get nice and golden brown). Toss with butter and season to taste with salt and pepper. Add in crispy shallots. Top with fresh herbs and a squeeze of lemon.