Combine chopped dates, boiling water, and baking soda in a bowl. Stir and let sit for 15–20 minutes to soften and release sweetness.
Preheat oven to 350°F (175°C). Grease an 8-inch square baking pan with butter or cooking spray.
In a medium bowl, whisk flour, baking powder, salt, and cinnamon. Set aside.
In a large mixing bowl, cream butter and brown sugar with an electric mixer until light and fluffy (3–5 minutes).
Beat in eggs one at a time, then mix in vanilla extract until combined.
Add soaked dates (with liquid) to the butter mixture and stir until blended. Fold in dry ingredients gently until just combined—don’t overmix.
Spread batter into prepared pan and bake 30–35 minutes, or until a toothpick inserted in the center comes out with moist crumbs.
In a saucepan, melt butter over medium heat. Add brown sugar and heavy cream. Stir until smooth and bubbling, about 3–4 minutes. Remove from heat and stir in vanilla.
Cool pudding for 10 minutes, then serve warm with hot toffee sauce. Top with ice cream, whipped cream, or nuts if desired.