Marinate chicken fillets in 4 tablespoons olive oil and Berbere spice mix. Refrigerate overnight or at least 4 hours.
Wash, core, and quarter fresh plums. Put in a saucepan with water covering them. Cook on medium heat for 6 minutes. Add powdered sugar and 1 teaspoon cinnamon. Simmer for 4 minutes. Drain carefully without stirring.
Place the tagine on the stovetop on low heat. Once warm, increase to medium heat.
In the tagine, combine 2 tablespoons olive oil, 2 diced onions, 1 teaspoon cinnamon, 20g ginger, 2 garlic cloves, salt and pepper to taste, and 200ml water. Bring to boil over medium-high heat.
Add marinated chicken fillets to the tagine. Cook covered on medium heat for 30 minutes.
Add 200g dried apricots, 200g prunes, and the cooked plums. Simmer for 10 minutes until chicken reaches 74°C (165°F) internally.