Prepare the Dates:

1. Soak the dates: Preheat your oven to 350°F (175°C). Grease a 9×9-inch square baking pan with butter or cooking spray, then line it with parchment paper, leaving overhang on two sides for easy removal. Place the chopped dates in a heatproof bowl and sprinkle the baking soda over them. Pour the boiling water over the dates and baking soda, stir gently, and let sit for 15-20 minutes to soften. The dates will absorb water and become very soft, and the mixture will darken—this is perfect!
2. Mash the dates: After soaking, use a fork or potato masher to roughly mash the date mixture. You want some texture remaining—not a completely smooth puree, but most of the dates should be broken down. Set aside to cool slightly.

Make the Cake Batter:

3. Cream butter and sugar: In a large mixing bowl, beat the softened butter and dark brown sugar together with an electric mixer on medium speed for 3-4 minutes until light, fluffy, and pale in color. This incorporation of air is important for a tender cake.
4. Add eggs: Add the eggs one at a time, beating well after each addition. The mixture should be smooth and well combined. Add the vanilla extract and mix until incorporated.
5. Combine dry ingredients: In a separate bowl, whisk together the flour, baking powder, and salt. This ensures even distribution of the leavening agents.
6. Alternate additions: With the mixer on low speed, add the flour mixture in three additions, alternating with the date mixture (beginning and ending with flour). Add about ⅓ of the flour, mix just until combined, then add half the date mixture, mix, then another ⅓ flour, remaining dates, and final ⅓ flour. Mix each addition only until just combined—don’t overmix or your cake will be tough.
7. Bake: Pour the batter into your prepared pan and smooth the top with a spatula. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs (not wet batter). The top should be set and spring back lightly when touched. Don’t overbake—this cake should be very moist.

Make the Toffee Sauce:

8. Combine sauce ingredients: While the cake is baking (or after it’s done), make the toffee sauce. In a medium saucepan, combine the heavy cream, butter, and dark brown sugar. Place over medium heat.
9. Cook the sauce: Bring the mixture to a gentle boil, stirring frequently with a whisk to dissolve the sugar and melt the butter. Once boiling, reduce heat to medium-low and simmer for 4-5 minutes, stirring occasionally. The sauce should thicken slightly and become glossy. It will thicken more as it cools.
10. Finish the sauce: Remove from heat and stir in the vanilla extract and sea salt if using. Set aside. You can keep it warm over very low heat, or reheat gently before serving.

Assemble and Serve:

11. Poke holes: When the cake comes out of the oven, let it cool in the pan for 5 minutes. While still warm, use a toothpick or skewer to poke holes all over the surface of the cake (about 20-30 holes). This allows the toffee sauce to soak in beautifully.
12. Pour sauce: Pour about half of the warm toffee sauce slowly over the warm cake, allowing it to soak into the holes. Let it sit for 5-10 minutes to absorb the sauce.
13. Serve: Cut into squares and serve warm, with extra toffee sauce drizzled over each portion. Top with vanilla ice cream or whipped cream if desired. The combination of warm cake and cold ice cream is absolutely divine!