Heat 2 tablespoons of the olive oil in a small skillet over medium heat until hot. Tilt the skillet to collect the oil in a small pool against the side of the pan. Drop in the jalapeños and cook until brown all over and cooked through, about 5 minutes. Let cool, then peel and seed (see Chef's Note).

Place 1 jalapeño and the roasted peppers in a blender with salt and pepper to taste, and puree until smooth. Taste and add the second jalapeño, if desired. The sauce should be noticeably spicy, as it will be flavoring 3/4 pound pasta. Add the garlic paste, if using. You should have about 1-1/4 cups sauce. Set aside.

Heat 1 tablespoon of the olive oil in a large sauté pan over medium-high heat until hot. Add the shrimp and spread them out in the pan so they sauté instead of boil. Season well with salt and pepper. Continue to sauté quickly just until they are cooked through and have turned pink, about 3 minutes. Remove to a plate with a slotted spoon. Discard any liquid left in the pan.

Add the remaining 1 tablespoon olive oil to the pan and heat over medium-high heat until hot. Add the garlic and sauté briefly until light brown. Stir in the oregano. Add the chicken stock and bring to a boil. Add the pasta and salt and pepper to taste. Reduce the heat to medium-low and simmer slowly, stirring occasionally so the pasta does not stick to the bottom of the pan, until the pasta is al dente, about 12 minutes.

When the pasta is ready, stir in the pepper puree. Return the shrimp to the pan just to reheat. Add the parsley and all but 1 tablespoon of the Parmesan. Stir again. Pour into a warm serving bowl or individual plates and dust with the remaining 1 tablespoon Parmesan. Serve immediately.