Preheat the oven to 140°C (285°F) with fan assistance. If your oven does not have a fan setting, see note 3. Prepare an 8-inch round cake pan (3 inches deep) by greasing the sides and lining the base with baking paper.
Sift together the plain flour, baking powder, salt, ground cinnamon, ginger, nutmeg, and allspice. Whisk to evenly distribute the dry ingredients, then set aside.
In a separate bowl, whisk together the eggs and oil until fully combined.
Once the fruit mixture is at room temperature, transfer it into a large mixing bowl. Pour in the egg and oil blend and fold gently using a spatula until integrated. The consistency will be dense; take time to incorporate fully.
Add in the walnut halves and the chopped dates (if not previously included in the boiled mixture). Stir just until evenly dispersed.
Introduce the sifted dry ingredients and gently fold until no visible streaks of flour remain. Avoid overmixing to preserve the cake’s tender crumb.
Pour the batter into the prepared pan, smoothing out the top. Tap the tin lightly against the countertop to eliminate any large air pockets. Bake in the preheated oven for 75–85 minutes, or until a skewer inserted into the center emerges clean.
Allow the cake to rest in the pan for 30 minutes. Then, run a thin-bladed knife along the edges to loosen, and invert the cake onto a wire rack, setting it right side up to cool.