Heat the oven to 400F. Wash and dry the potatoes, poke them a few times with a fork, then rub them with 1 tbsp of the oil and half the salt. Bake until a fork slides through easily. Start checking at 35 minutes. Bigger potatoes can take closer to an hour.

While the potatoes bake, cook the bacon and drain it on a paper towel. Save the bacon fat. Slice the chives, grate the parmesan, and get a bowl of ice water ready.

Let the potatoes cool for about 5 minutes so they're easier to handle. Cut them in half lengthwise and scoop the insides into a bowl, leaving about 1/4 inch of potato in the skin so it holds its shape. Save the scooped potato for the sauce.

Brush the insides of the skins with the bacon fat (or the rest of the oil) and sprinkle with the rest of the salt. Put them cut side up on a sheet pan and bake at 400F for 10 minutes to firm up.

Cook the noodles in boiling water for 3 minutes. Save 1/4 cup of the noodle water, then drain the noodles and put them in the ice water. Drain again once they're cold.

Put both packets, 1/4 cup of the noodle water, and all of the scooped potato in a tall container and blend with an immersion blender until smooth. No blender? Mash the potato with a fork and whisk it in a little at a time. Taste it and add salt. The packets are meant for one pack of noodles, so with all the potato it'll probably need more salt than you think.

Toss the drained noodles in the sauce until they're all coated.

Fill the skins with the noodles and grate parmesan over the top. Bake at 400F for 8 to 10 minutes, just until the cheese melts. Don't leave them in too long, or the noodles on top will dry out.

Chop the bacon and top each half with bacon, a spoonful of sour cream, and chives. Serve right away.