In a saucepan, combine the brown sugar and butter.
Cook over medium heat, stirring until the butter melts and the sugar dissolves.
Simmer for 2–3 minutes and Stir in the vanilla extract and salt.
Pour in the heavy cream and whisk until smooth and fully combined.
In a bowl, Add granulated sugar, cornstarch, salt, egg yolks, and vanilla extract.
Mix until well combined.
Gradually whisk in the whole milk until smooth.
Transfer the mixture to a saucepan and cook over medium-low heat, whisking constantly until thickened.
Remove from the heat and stir in the cubed butter until completely melted.
Transfer the custard to a bowl, cover the surface with plastic wrap, and let it cool completely.
In a saucepan, combine the butter and chopped dates. Cook over medium heat for 2–3 minutes, stirring occasionally until the dates soften.
Transfer the warm date mixture to a large mixing bowl and beat until mostly smooth.
Add the egg yolks and vanilla extract. Mix until well combined.
Add the light brown sugar and beat until the mixture is smooth and creamy.
Continue mixing until the wet ingredients are evenly combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture and mix until just combined.
Continue mixing until a soft cookie dough forms with no dry flour remaining.
Scoop equal portions of dough onto a parchment-lined baking sheet, leaving about 2 inches between each cookie.
Bake in a preheated 350°F (175°C) oven for 10–12 minutes, or until the edges are lightly golden.
Let the cookies cool completely on a wire rack.
Remove the plastic wrap from the Vanilla Custard Buttercream, add the heavy cream, and beat until smooth and creamy.
Transfer the vanilla custard buttercream to a piping bag fitted with your preferred piping tip.
Pipe the vanilla custard buttercream onto each cooled cookie in a decorative swirl.
Drizzle the cooled toffee sauce over the buttercream and serve.
