Preheat the oven to 450°F and move the oven rack to the middle-lower position.
Prepare Baking Sheet: Spray a heavy-duty baking sheet generously with nonstick cooking spray. Set aside.
Add the pork: Lay the already marinated pork tenderloin on the tray, down the center.
Prepare the veggies: Chop broccoli into florets and arrange them on one side of the baking sheet.
Prepare the potatoes: Cut into fourths, and arrange them next to the broccoli, cut side down.
Season: Drizzle with some olive oil and season with salt and pepper.
Roast: Place the sheet pan in the oven and roast for 20–25 minutes, or until the thickest part of the pork reaches 140°F on a meat thermometer.
Make the maple dijon garlic butter: Meanwhile, while the pork roasts, mix together butter, garlic paste, maple syrup, dijon mustard, chives, salt, and pepper until smooth.
Finish and rest: Remove the sheet pan from the oven. Top each tenderloin with 2 tablespoons of garlic butter mixture and let the pork rest for 5 minutes before slicing. Remove broccoli from the oven as well.
Finish Potatoes: Top potatoes with some of the butter mixture. If potatoes aren't tender enough, return to the oven to finish cooking, about 10 minutes.
Serve: Toss the remaining maple dijon garlic butter with the potatoes and broccoli. Slice the pork and serve everything hot.