Preheat the oven to 400 degrees F.
Use a sharp knife to cut a “pocket” into the side of each chicken breasts. I do cut from top to bottom so the asparagus can fit, but don’t cut the whole way through - you don’t want to fully butterfly it. If you do by accident - it’s fine! Because we’re going to wrap it in prosciutto.
Sprinkle the chicken all over, inside and out, with salt and pepper. Stick 2 ounces of brie cheese inside the pocket of each chicken breast. Stick 3 to 4 asparagus spears in next. Wrap the chicken breast with a slice or 2 of prosciutto. I find that 2 slices really works best to hold everything (the cheese!) inside.
Heat the olive oil in an oven-safe skillet over medium heat. Add the chicken breasts to the skillet and cook until the prosciutto is crispy on both sides, about 3 to 4 minutes per side. Pour the stock in the skillet.
Transfer the skillet to the oven uncovered and roast for 10 to 15 minutes, or until the internal temperature of the chicken reaches 165 degrees F. Make sure the thermometer is in the chicken and not in the brie!
Serve immediately with the scallion smashed potatoes.