Season the chicken thighs generously with salt and pepper, then set aside.
Heat a skillet over medium-high heat and add oil. When shimmering, add the chicken thighs and sear for about 3-4 minutes per side until golden brown. This step builds flavor and creates a rich crust.
While the chicken is searing, roughly chop the mushrooms and mince the garlic. The mushrooms will release their earthy aroma as they cook, deepening the dish's flavor.
Add the sliced mushrooms to the skillet and sauté for 2-3 minutes until they start to soften and release their moisture, filling the kitchen with a rich, earthy scent.
Transfer the seared chicken and sautéed mushrooms into your slow cooker. Pour in the chicken broth and add a sprig of thyme or rosemary if desired, which infuses the dish with fragrant herbal notes.
Set the slow cooker to low and cook for 6-8 hours. The chicken becomes tender and easily shreds, while the mushrooms soften and absorb the savory broth, creating a velvety, earthy sauce.
Once the cooking time is up, check that the chicken is fork-tender and the mushrooms are oozy. Remove the sprig of herbs if used.
If you want a richer, creamier sauce, stir in sour cream or heavy cream now and let it sit uncovered for 10 minutes to thicken slightly.
Gently shred the chicken with two forks directly in the slow cooker or transfer it to a plate and shred, then return to the sauce. The dish should look velvety, with mushrooms oozing into the sauce.
Taste and adjust the seasoning with additional salt and pepper if needed. Serve hot, spooning the earthy, savory mixture onto plates and garnishing with fresh herbs if desired.
