In a shallow dish, combine the flour, salt, black pepper, garlic powder, and paprika.
Place each chicken breast between two sheets of plastic wrap and gently pound to about 1/2 inch thickness.
Dredge each chicken breast in the seasoned flour mixture, shaking off any excess.
Layer two slices of ham and two slices of Swiss cheese on top of each chicken breast.
Roll up each chicken breast tightly and secure with toothpicks if needed.
Melt the butter in a large skillet over medium heat.
Sear the chicken rolls on all sides until golden brown, about 2 minutes per side.
Transfer the seared chicken rolls to the crock pot.
In a bowl, whisk together the chicken broth, heavy cream, and Dijon mustard.
Pour the sauce mixture over the chicken in the crock pot.
Cover and cook on low for 4 to 4 1/2 hours, or until the chicken is cooked through and tender.
About 15 minutes before serving, remove the chicken from the crock pot and keep warm.
In a small bowl, mix the cornstarch and cold water until smooth.
Pour the cooking liquid from the crock pot into a saucepan and bring to a simmer over medium heat.
Whisk in the cornstarch slurry and cook until the sauce thickens, about 2 minutes.
Pour the thickened sauce over the chicken rolls.
Garnish with chopped fresh parsley and serve hot.