In a shallow bowl, combine the flour, garlic powder, onion powder, salt, and black pepper.
Pound each chicken breast to about 1/2 inch thickness using a meat mallet or rolling pin.
Place 2 slices of ham and 2 slices of Swiss cheese on each flattened chicken breast.
Roll up each chicken breast tightly and secure with toothpicks to hold the filling inside.
Dredge each rolled chicken breast in the seasoned flour mixture, coating all sides evenly.
Heat olive oil in a large skillet over medium-high heat.
Add the chicken rolls and brown on all sides, about 2-3 minutes per side.
Transfer the browned chicken rolls to the crock pot.
In a medium bowl, whisk together chicken broth, heavy cream, Dijon mustard, and Parmesan cheese until smooth.
Pour the sauce over the chicken rolls in the crock pot.
Cover and cook on low for 4 hours, or until the chicken is cooked through and tender.
About 15 minutes before serving, mix cornstarch and water in a small bowl to create a slurry.
Stir the slurry into the crock pot sauce to thicken it.
Replace the lid and cook for an additional 15 minutes.
Remove toothpicks from the chicken rolls before serving.
Garnish with chopped fresh parsley and serve warm.