1. Preheat oven to 350F.

2. Clean potatoes thoroughly. Skewer them vigorously a few times with a fork. Coat the outsides with oil, salt, and pepper.

3. Bake for 90-120 minutes.  Start checking at 90 minutes.  When they're done, the skins will feel crunchy and the insides when you squeeze them gently will feel slightly squidgy.

4. When done, remove from oven.  Cut each potato in half; scoop out the innards and put in a bowl.  Leave the shells on a grill pan or cooling rack or similar.  The quicker you finish this step, the better for the skins - if the potatoes sit around whole for too long, the skins will lose their crunch.

5. Press the innards through a potato ricer into another bowl.  

6. Add melted margarine and stir until mixed in (the mixture will go clumpy). Add a little milk (perhaps 2T) and mix in; repeat as necessary until the potato is a smooth, non-sloppy consistency.

7. Add any seasonings and cheese you desire at this point and mix in.  If you wish to have your cheese melted on top instead, wait til step 9.

8. If you have more than 25 minutes between now and serving time, leave the mixture in the bowl until 25 minutes before serving time.

9. At that point, scoop the filling into the potato shells.  If you want cheese melted on top of the potatoes, then place some shredded cheese on top now.

10. Replace potatoes on the grill pan; put back in oven 20-25 minutes until the top has formed a skin and the edges are slightly brown.