Preheat oven to 375° F. Lightly grease four 6-ounce ramekins and place on a baking sheet. Filling may bubble over, so you can line baking the sheet with foil for easy clean up, if desired.
In small bowl, mix together filling ingredients and divide evenly between your ramekins.
Place the topping ingredients in another bowl and use a pastry blender (or a fork) to crumble/cream your ingredients together until coarse meal forms.
Divide topping evenly among each ramekin and place in the oven for 25 minutes. If you like a crispy top, you can turn the broiler on for 2 - 3 minutes at the very end, but watch very carefully if you do this so it does not burn!
Recipe by Gluten-Free Homemaker at https://glutenfreehomemaker.com/plum-crumbles/