Make the cake: Pit and roughly chop dates and place them in a heatproof bowl. Pour boiling water over them and stir in the baking soda. Cover the bowl and set it aside for 30 minutes.

Meanwhile, heat oven to 350°F (175°C). Butter a 9×13-inch baking pan. (I used a 9 inch square pan and added an extra 10 minutes of baking time.  It just makes for a taller cake and a few less serving pieces)  As an extra precaution, if you’re nervous about sticking (although this cake should not), you can line the bottom with a fitted rectangle of parchment paper.

Blend date-water mixture in a blender or food processor until smooth. In a large bowl, combine the melted butter and sugars. Whisk in eggs, then salt. Stir in the flour, then date puree. Pour the batter into the prepared pan and bake for 25 to 30 minutes, until a toothpick inserted into the center comes out clean.

If you’d like to transfer it later to a serving plate, let cool in the pan for 20 minutes, then flip it out onto a cooling rack, removing the parchment paper if you used it.

Make the sauce: Combine butter, cream, sugar and vanilla in a larger saucepan than you think you’ll need as the mixture bubbles up.  Cook over medium heat and bring to a simmer. Whisk for about 10 minutes, until the mixture thickens slightly.

To serve: Cut the cake into squares (still warm is just fine). Drizzle each slice with toffee sauce, a pinch of sea salt, and top with a dollop of whipped cream, if desired.