Add strawberries, sugar*, pepper, grapefruit juice, and water*.
Heat over medium heat until strawberries are soft.
Mash ingredients together using a fork or spoon.
Heat until thickened.
Slice each chicken breast into tenders.
Grill until almost cooked through.
Top with strawberry shallot jam and finish grilling.
Notes
If using frozen strawberries, add 1 additional teaspoon sugar.
Also, if using frozen strawberries, you may not need to add water. Cook the mixture a bit and only add water if it gets too dry before strawberries are cooked down.