In a medium bowl, combine peeled shrimp with olive oil and Cajun seasoning. Toss to coat the shrimp evenly with the spices and set aside to marinate for about 10 minutes.

Boil salted water in a large pot and cook the fettuccini for 8-10 minutes until al dente. Once cooked, drain the pasta and set it aside, tossing it lightly with a bit of olive oil to prevent sticking.

In a large pan over medium heat, melt the butter. Add in the sliced mushrooms and chopped shallots; sauté them until they are tender and fragrant, about 5 minutes, then remove from the pan and set aside.

In the same pan, add the marinated shrimp and cook for 2-3 minutes until they turn pink and are cooked through. Set them aside with the sautéed vegetables.

Pour ⅔ cup of chicken broth into the pan and bring it to a boil. Reduce to a simmer, allowing it to concentrate and reduce to about ¼ cup over 2-3 minutes.

In a small bowl, mix the sour cream with cornstarch and the remaining 1 cup of chicken broth until smooth. Stir this mixture into the reduced broth in the pan, cooking until it thickens and bubbles for about 1 minute.

Return the cooked shrimp, sautéed vegetables, roasted red bell peppers, and capers (if using) back into the pan. Mix everything well to combine, heating through and seasoning with salt and pepper as needed.

Plate the cooked fettuccini and generously top it with the Blackened Shrimp Stroganoff mixture. Enjoy immediately for a comforting meal!