Heat 1 tablespoon butter in a large skillet over medium-high heat. Season the chicken thighs generously with salt and pepper. Sear for 2–3 minutes per side until golden brown. Transfer to the slow cooker.
In the same pan, reduce the heat to medium and add the remaining tablespoon of butter. Add the leeks, celery, garlic, red chili flakes and a generous pinch and salt and pepper. Cook for 4–5 minutes until softened.
Pour in the white wine, scraping up any browned bits from the bottom of the skillet. This adds great flavor and makes the pan easier to clean! Bring to a simmer and cook for 3–5 minutes until reduced by about half. Transfer everything to the slow cooker.
Add the chicken broth, lemon juice, artichoke hearts and potatoes if using. Stir gently to combine. Cover and cook on low for 4–5 hours or high for 2–3 hours, until the chicken is tender and cooked through.
Shred into large chunks using two forks. Add the softened cream cheese, stirring until completely melted into the broth. Stir in the fresh spinach until wilted then stir in the dill.
Season with salt, pepper or lemon juice to taste. Top with sliced green onions and freshly grated Parmesan.
