Preheat the oven to 425 degrees . Line a baking sheet with parchment paper. Place the potatoes cut side down on the baking sheet and brush the skins with 1 tablespoon olive oil. Bake until tender, about 30 minutes; cut in half lengthwise and let cool slightly. Scoop out the potato slices into a medium pot, leaving 1/4-inch-thick shells. Place the shells cut side up on the baking sheet and brush all over with the remaining 2 tablespoons olive oil. Add the milk and butter to the potatoes in the pot and mash until smooth. Stir in half of the parmesan and one-quarter of the salami.
In a small bowl, toss the remaining parmesan and salami with the bread crumbs. Press some of the mixture into each of the potato shells. Bake until crisp and golden, 20 to 25 minutes.
Meanwhile, in a small bowl, combine the sour cream and jalapenos; season with salt. Reheat the mashed potato mixture and mound onto each baked potato skin. Top with the jalapeno sour cream; serve warm.