Combine garlic powder, salt, black pepper, rosemary, and sage in a small bowl and rub evenly over the pork tenderloin.
Heat olive oil in a skillet over medium-high heat and sear the pork on all sides until golden brown, about 3 to 4 minutes per side.
Place the seared pork in the slow cooker and pour chicken broth around it, taking care not to wash off the seasoning.
In a separate bowl, whisk together Dijon mustard, butter, and white wine until smooth, then pour over the pork in the slow cooker.
Cover the slow cooker and cook on low for 6 to 8 hours until the pork is tender and easily shreds with a fork.
Remove the pork from the slow cooker and set aside. In a saucepan, whisk cooking liquid with heavy cream and flour over medium heat until the sauce thickens.
Stir in chopped thyme and parsley, then slice the pork and drizzle the creamy Dijon sauce over each portion before serving.