1) To make the filling: Preheat the oven to 180°C. Prepare round baking tin. Melt in it butter, add sugar. Stir together until the sugar is well mixed into the butter.
2) Arrange the dates attractively, curved-side up, in the butter/sugar mix. Place the walnut halves into date cavities.
3) To make the sponge cake: Beat the eggs and sugar in a mixing bowl. Add the flour and baking powder. Mix until just combined. Pour in the milk and mix once again.
4) Pour the batter over the dates and bake for about 35-40 minutes.
5) To make the caramel sauce: pour 1/2 cup water into a medium heavy-bottom saucepan. Add sugar and cook over medium heat, gently stirring occasionally, until sugar is dissolved. Continue to cook, without stirring, until syrup comes to a boil. Let syrup boil, gently swirling pan occasionally, until it has almost turned medium amber colour.
6) Remove from heat, and carefully pour in cream (caramel will bubble). Add vanilla and salt, and stir with a clean wooden spoon until caramel is smooth.
7) While the cake is still hot use a thin knife or a trussing needle to pierce the cake.
8) Pour hot caramel sauce over the cake in several additions. Distribute the sauce with the spoon.
9) Serve warm with a scoop of vanilla ice cream.