Place dates and water in a small sauce pan. Simmer until most of the water is absorbed by the dates, about 15 minutes. Remove from heat and place dates and remaining water into a food processor. Pulse until the dates are completely minced. Set aside.
Preheat oven to 350 degrees. Whisk flour, baking powder, baking soda, and salt together in a medium bowl. Set aside. Add butter and brown sugar to the bowl of a stand mixer. Beat on medium until light and fluffy, about 2 minutes. Add egg and vanilla extract and mix until combined. Add in the date puree and mix until combined. Add dry ingredients and mix just until combined.
Grease 6 small ramekins (about 6-8 ounces) with nonstick spray. Place on a baking sheet. Spoon 1/2 cup of the cake mixture into each of the 6 ramekins and smooth the top so it's in an even layer. Place baking sheet with 6 filled ramekins into preheated oven. Bake until cooked through, about 20 minutes.
Remove cakes from oven but keep oven on. Let them cool for 5-10 minutes and then remove the cakes from the ramekin. Slice each cake in half. Place 1 tablespoon of toffee sauce into empty ramekin, Add one half of the slice cake. Spoon another tablespoon over the cake half. Top with other half of cake and finish with one more tablespoon of toffee sauce. Repeat with other five cakes.
Place cakes back into over to bake for 10 more minutes, or until the toffee sauce is bubbling around the sides. Remove from oven and invert onto a plate for serving. Serve with ice cream, whipped cream, or by themselves. Best served warm.