First, prepare the plum puree.
Combine 1 cup California dried plums (about 18 plums) and 6 tbsp hot water in a food processor.
Process until smooth and transfer to a measuring cup and set aside.
Now prepare the marinade for the chicken.
Combine 1/4 cup coconut sugar, 1/4 cup olive oil, 1/2 cup plum puree, 1/2 cup balsamic vinegar, minced garlic, 1/4 cup lemon juice, 1 tbsp Mediterranean seasoning blend in a large bowl. Season with a little salt and pepper, to taste.
Whisk to combine, the marinade should be thick, like barbecue sauce.
Add chicken breasts to marinade and pour into a sealed container.
Refrigerate for 2-3 hours for flavors to mingle and meat to tenderize.
Toast pine nuts in a skillet over medium-low heat until lightly golden and fragrant. Set aside to cool.
Preheat grill, then turn down to medium heat.
While grill is heating, prepare your sauce.
Finely chop remaining 1/4 cup California dried plums and place into a small saucepan. Add 2 tbsp balsamic vinegar, 2 tbsp coconut sugar, 2 tbsp plum puree and 2 tbsp lemon juice. Cook on medium heat until mixture starts to bubble and thicken. Remove from heat and stir in 2 tbsp butter. Set aside while you grill the chicken breasts.
Cook chicken until internal temp is 160 degrees F, turning several times and basting with remaining marinade. Allow to cook for a few minutes after final basting. Cooking time will vary with the size of the chicken breasts. I flipped the breasts about every 2 minutes and basted for a total of 4 rotations. They were good and saucy!
Serve each chicken breast with about 2 tsp plum sauce and top each serving with toasted pine nuts.