The Mutton chops style of beard are actually a fancier term for longer sideburns that are allowed to extend down to the corners of the mouth.
To grow Mutton Chops, a man should let his sideburns grow to the corner of his mouth freely.
Then, he should terminate a part of the sideburns, creating an imaginary line defined at each corner of the mouth.
The bottom edge of the sideburns should be clearly defined along the edge of the jawline.