For the cake:
Preheat the oven to 350 degrees.
Oil a 8-inch x 8-inch square cake pan and line with parchment paper.
In a saucepan, add dates and water, and bring to a boil, then turn the heat off; cover and let sit for 10 minutes.
Blend date-water mixture to a smooth paste and set aside.
In a stand mixer, beat butter and sugar at medium speed until batter resembles a thick homogeneous dough, about 2 to 3 minutes. On medium-low speed, add in the egg and vanilla and beat until fully incorporated. Slowly add in the date puree and mix until combined. Reduce the speed to low, and slowly add in the flour, baking powder, baking soda, and salt until just barely combined. Batter will be thick, like buttercream frosting.
Pour into the cake pan and bake for 30 to 35 minutes, until a toothpick comes out with just a few crumbs. Remove from the oven and transfer to a cooling rack. Once cooled to room temperature, cut into 1-inch cubes.
For the date-toffee sauce:
In a small saucepan over low heat, melt butter and whisk in brown sugar and date syrup until combined. Increase heat to medium, and once bubbling, add heavy cream and vanilla extract. Bring to a boil, then simmer for 3 minutes until slightly thickened (it will continue to thicken as it cools). Season with flaky salt and let cool to room temperature.
For the skyr cream:
In a stand mixer, whip skyr, cream, sugar, and vanilla extract on high speed until stiff peaks form. Keep in the refrigerator until ready to use.
To assemble the trifle, layer cake cubes on the bottom of a trifle bowl, then drizzle with the date-toffee sauce. Dollop a layer of whipped cream on top, then repeat, layering pieces of cake, followed by the toffee sauce and whipped cream. Don’t have a trifle bowl? You can easily use individual glasses or dessert cups.