Make chicken: In a blender or food processor, combine preserves, onion, ginger, oil, tamari and garlic. Purée until combined but not completely smooth; mixture should still have some small chunks. Pour into a large zip-top freezer bag or freezer-safe glass container. Add chicken, seal and shake to combine. Open bag, press out as much air as possible, seal and freeze for up to 2 months.To cook chicken, remove bag from freezer and let stand in the refrigerator for 24 hours, or until fully thawed. Transfer to a slow cooker and cook on high for 5 to 6 hours or on low for 8 hours. Season with salt and pepper (if using).Make greens: About 5 minutes before serving, in a large skillet, heat oil on medium. Add garlic and greens; cook, stirring, until garlic is fragrant and greens are wilted, 2 to 3 minutes. Sprinkle with sesame seeds.To serve, divide greens among plates; divide chicken and sauce over top. Garnish with green onions.