In a medium saucepan, combine 1 1/4 cups of the heavy cream, butter, corn syrup, and sugar together; bring to a boil. Cook over medium-low heat, stirring frequently until a deep amber color forms (about 40 minutes). Carefully whisk in the remaining cream. Strain the sauce through a sieve into a bowl.
In a small saucepan, simmer the dates in water until the water is nearly absorbed and the dates are soft (about 15 minutes). Transfer the dates and any remaining liquid to a food processor and puree until very smooth.
Preheat oven to 350. Lightly butter six 1/2 cup ramekins (or a muffin tin). In a small bowl, whisk the flour with baking powder, baking soda, and salt.
In a medium bowl, beat the butter and brown sugar together with an electric mixer until well combined. Beat in the egg and vanilla at medium speed until light and fluffy. Then beat in the cooled date puree. At a low speed, beat in the dry ingredients until combined.
Spoon the batter into the ramekins (or muffin tins) and smooth over the tops. Bake for 20 minutes, or until a toothpick inserted into the center comes out clean. Let cool slightly.
Let cakes cool for a few minutes, then invert onto a baking rack. When ready to serve, spoon toffee sauce over the cakes. If desired, put back into the oven to warm while the toffee sauce soaks into the sponge.
