1. Begin by making the sticky toffee pudding. Position a rack in the center of the oven and preheat to 350°F convection, 375°F standard.
2. Add 8 ounces of dates and 1 teaspoon of baking soda to a heat-proof cup or bowl. Cover with 1 cup of boiling water and let sit.
3. Add 85 grams of softened butter to a bowl with 175 grams of brown sugar. Beat until fluffy, then add 1/2 teaspoon vanilla extract and two eggs. Beat again until smooth.
4. Either using your hand mixer or a blender, mix the dates together with the water they are soaking in to form a paste. Add this to the bowl with the wet ingredients and mix.
5. Add 210 grams of flour, 1 1/2 teaspoons baking powder, 1 teaspoon kosher salt, 1/2 teaspoon ground cinnamon, 1/4 teaspoon ground clove and 1/4 teaspoon nutmeg. Mix this all together to form a smooth batter.
6. Pour the batter into a lined 9x9-inch baking dish and bake for 30-33 minutes or until you can insert a toothpick in the center and it comes out clean. Set this aside to cool.
7. Next, make the tiramisu filling. In a large bowl, whip together 4 egg yolks and 50 grams of sugar until nearly tripled in size. It will go from a deep yellow color to very pale yellow (this is crucial to a not-runny tiramisu). Set aside.
8. In another bowl, whip 175 grams of heavy cream and 50 grams of sugar into stiff peaks. Gently fold in the mascarpone and 1/4 teaspoon ground cinnamon.
9. Fold the egg mixture into the whipped cream mixture, aiming to keep it as fluffy as possible. Store in the fridge until you are ready to use it.
10. Now make the toffee. Set a medium pot over medium heat and add 200 grams of sugar and 1/4 teaspoon each of cinnamon, clove, all spice and nutmeg. Stir occasionally, letting the sugar melt and darken from white to a nice golden color. Make sure not to let the bottom burn.
11. When the sugar is golden and fully melted add the butter all at once. Stir vigorously to let the butter emulsify. It will take a few minutes, but the mixture should turn into a smooth caramel.
12. Add in 120 grams of heavy cream and immediately turn off the heat. This will steam a bit so watch your hands, then whisk it into a smooth toffee. Keep this off the heat so that it doesn't firm up into a caramel. Whisk in 1/4 teaspoon of kosher salt and set aside.

To assemble the tiramisu:

1. Let the sticky toffee pudding cake cool until it is easy to handle. The longer the cooling time the easier it will be to slice. Use a serrated knife to slice it across the center into two square layers.
2. Add one layer of the cake, cut-side-up, to a 9x9-inch baking dish. If you are using the rum, brush 1-2 tablespoons into the cake. Use a cookie scoop to scoop the toffee onto the cake and spread it out to the edges with a knife. Repeat this with the mascarpone mixture.
3. Layer the next cake layer on top and repeat, finishing with a smooth mascarpone layer as the topping. Reserve any extra toffee for serving.
4. This will keep in the fridge for 12 hours up to two days, but you could also serve it immediately. Dust with cinnamon before slicing and serving!