Preheat oven to 350°F (175°C). Grease and flour an 8-inch square baking pan.
In a bowl, combine chopped dates and hot water. Stir in baking soda and let stand for 5 minutes.
In a separate bowl, cream together softened butter and brown sugar until light and fluffy. Beat in eggs one at a time, then stir in the date mixture.
Gradually blend in flour and baking powder. Pour batter into prepared pan.
Bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
While cake is baking, prepare the toffee sauce. In a saucepan, melt butter over medium heat. Stir in brown sugar and heavy cream. Bring to a simmer, stirring constantly, and cook for 2-3 minutes until slightly thickened. Remove from heat and stir in vanilla extract.
Poke holes in the warm cake with a fork and pour the toffee sauce over the cake. Let it soak in for a few minutes before serving.
Notes
Serve warm with a scoop of vanilla ice cream or whipped cream for an extra indulgent treat.