Preheat oven to 400 degrees F. 

Make 20 horizontal slits in the top of the pork tenderloin, spacing them evenly apart. 

Add a slice of garlic to each slit, a pinch of thyme leaves, and a pinch of chopped fresh rosemary. Season tenderloin evenly with salt and pepper. 

Add oil to a cast iron skillet over medium-high heat. Once hot, add pork tenderloin and sear on all sides until browned. 

Add cranberries to the skillet. Place skillet in the oven and roast for 15 to 20 minutes. 

Remove skillet from oven and place pork tenderloin and cranberries on a serving platter, tenting with aluminum foil to keep warm.

Place skillet back over medium-high heat. Add wine, thyme sprigs, and rosemary sprigs to the skillet. Bring to a simmer and use a wooden spoon to scrape up the bits on the bottom of the pan. 

In a small bowl, stir together cornstarch with water until combined.

Pour cornstarch slurry into the skillet and simmer until the mixture is thickened. Add chicken stock and sugar, stirring to combine and bringing to a simmer. Simmer until thickened. Season with salt and pepper to taste. 

Pour sauce over pork tenderloin and serve.