Mix the butter, Dijon and fresh basil in a small bowl.
Preheat barbeque or broiler; brush grill or broiler pan with vegetable oil. Season the fish with salt and pepper. Grill fish just until cooked through, 3 to 4 minutes per side.
Transfer the swordfish to plates and top each with a spoonful of the mustard basil butter. Garnish with basil sprigs.
Notes
If you are preparing this recipe as GLUTEN-FREE, just be sure to use a brand of Dijon that is known to be GF.
Reduce fat and calories by reducing how much sauce you choose to put on your swordfish.