Pour ¾ cup boiling water over dates in a small heatproof dish. Make sure dates are submerged; cover and let stand until softened, about 10 minutes. Pour dates and soaking water into a food processor; puree until smooth, about 30 seconds. Refrigerate ½ cup date puree in an airtight container until ready to use. Whisk together remaining 1 cup date puree, 4 cups cool water, and vanilla extract in a large bowl until smooth. Set aside. 2.

Place ¼ cup oats, 1 teaspoon brown sugar, ¼ teaspoon cinnamon, ¼ teaspoon salt, and a pinch of nutmeg into each of 4 (12- to 16-ounce) glass jars. Pour reserved date-water mixture evenly into each jar (about 1 ¼ cups per jar); stir until combined.

Place uncovered jars inside a 6- to 7-quart slow cooker. Pour additional water into slow cooker around jars until water reaches about two-thirds up sides of jars. Cover and cook on low until oatmeal is tender and thickened, 8 to 9 hours. (If jars are too tall and slow cooker lid does not close, cover slow cooker tightly using aluminum foil.) Carefully remove jars from water; stir oatmeal mixture until combined. (Oatmeal will have separated into layers.)

Just before serving, melt butter in a small skillet over medium, stirring often. Add maple syrup, reserved ½ cup date puree, and remaining ¼ teaspoon salt. Cook over medium, whisking constantly, until well combined and creamy, about 1 minute. Remove from heat. Serve oats topped with maple-date sauce, and drizzle with cream. Serve with fresh berries, nuts, and/or dried fruit (if using).