Begin by slicing the chicken breasts into 1-inch chunks, then season lightly with salt and pepper.
Heat a large skillet over medium-high heat and add a tablespoon of oil. Once shimmering, add the chicken pieces and sear until golden brown on all sides, about 3-4 minutes. Transfer the browned chicken to the slow cooker.
In the same skillet, add sliced onions and minced garlic. Cook for about 2 minutes until fragrant and slightly translucent, scraping up any browned bits from the bottom.
Transfer the sautéed onions and garlic to the slow cooker, then add sliced cremini mushrooms, beef broth, smoked paprika, and a pinch of salt. Stir everything together to combine.
Cover the slow cooker and set it to low. Let it cook gently for about 4 hours, until the chicken is tender and the flavors meld into a rich, fragrant sauce.
About 15 minutes before serving, stir in the sour cream to create a silky, tangy sauce. If it looks too thick, add a splash of hot broth or water to loosen it up.
Once the sauce is smooth and creamy, turn off the slow cooker and let it sit for 5 minutes to allow the flavors to settle.
Cook your egg noodles according to package instructions until al dente, then drain.
Serve the tender chicken and mushroom sauce over the hot noodles, garnished with fresh herbs if desired, and enjoy your cozy, creamy dinner.
