Preheat oven to 400F/204C degrees. **Par-cook potatoes by piercing each one several times with a fork or knife tip and bake until tender, about 45 minutes. Allow potatoes to cool slightly.
Peel the potatoes, if desired, and cut in half lengthwise, then cut each half into 1/4" slices. Set aside.
In a large skillet over medium-high heat, heat 2 tablespoons of butter/fat until melted. Add half of the potatoes and sauté until light brown, about 4 to 5 minutes. Add half of the onions and a little salt and pepper, then continue cooking until potatoes are a golden brown and onions are just cooked through, about 7 to 8 minutes. Remove from pan and set aside to keep warm. Repeat the process with the remaining potatoes and onions.
When all potatoes and onions are cooked, toss with the fresh chopped parsley and serve immediately.
For fluffy potatoes, par-cook using one of the following methods:
bake (in a 400F/204C degree oven for 45 minutes)
boil in salted water (for 5 minutes on high heat; drain and dry slices before using)