In a large skillet, warm the 3 tablespoons olive oil over medium-high heat.
Toss in the 1 medium leek, season with salt, and sauté until soft and translucent, about 3 minutes.
Add the 1 pound store-bought fresh tortellini or tortelloni to the skillet, pour in the ½ cup water--careful here because there could be a big whoosh of steam--and immediately cover the pan.
Let the tortellini steam, stirring occasionally, until all the water has been absorbed by the pasta, about 5 minutes.
Bump the heat to high.
Add the 1 ¼ cups heavy cream, 4 ounces prosciutto matchsticks, ¾ cup frozen sweet peas, and 2 ounces finely grated Parmigiano-Reggiano. Let the sauce cook, stirring frequently, until it thickens, 2 to 3 minutes.
Slide the pan off the heat, season with salt, if needed, and a good sprinkling of freshly ground black pepper. The sauce will continue to thicken.
Serve in heated bowls with plenty more cheese.