Sumo Wrestler

While most monastic traditions rely on speed, elegance, grace and wisdom.  You are an entertainer.  Your body isn't built for aesthetics, it is built for one of the most noble of combat sports.  An armour of muscle, covered in an even thicker armour of fat.  While most people might see you as unhealthy, obese and the likes you are almost the exact opposite, a specimen at the peak of physical performance.

Armour of fat

You have built up an armour of muscle and fat, absorbing some of the impact from bludgeoning attacks.

Replace your wis modifier with your con modifier for the sake of the Monks unarmoured AC.

Unstoppable Force, Immovable Object

You gain advantage when you take the grapple or shove action as part of your attack action, and you have advantage to resist grapple and shove actions performed against you.

In addition, you may shove the target as part of your attack.  Roll your attack action as normal, and then perform the shove action if the attack roll is successful.  If the target is moved 5ft back you may move 5ft with them.  This will not trigger attacks of opportunity from nearby enemies.

Chanko Nabe

Over time you have perfected your recipe for Chanko Nabe.  

During a long rest you can cook a meal of Chanko Nabe, a hearty stew packed with meat and vegetables, and a staple of the sumo wrestlers diet.  

Each person who eats the stew will be filled with renewed vigor giving them resistance to being frightened, as well as granting 2d10+con temporary HP for the next 24hours.

Body Slam

When an opponent is grappled, you may choose to perform a powerful body slam.

Perform a grapple check against the already grappled opponent.  If you succeed, the opponent is lifted off their feet and slammed into the ground, with the full force of your bodyweight behind it.  The opponent is then prone and must make a Con save.

On a failed save they take 20d10 damage and are incapacitated for 1d4 rounds.
On a successful save they take half as much damage and are not incapacitated.