[The day before]
Prepare the topping of rum raisins. Add rum to raisins, mix, and cover with plastic wrap. Leave at room temperature overnight or more.

[Cake]
(Preparation)
・Preheat an oven to 200℃ / 392 F.
・Line a cake pan with parchment paper.
・Soak the raisins and dried berries in lukewarm water for 15 minutes, then drain and pat dry with a paper towel.

Cream unsalted butter until smooth, add cane sugar in three batches, and mix well each time. Use an electric hand mixer to beat it on low speed for 3 minutes.

Add the beaten egg in two batches, and beat it on low speed until smooth each time. Add vanilla oil and mix.

Stir well cake flour, baking powder, and cinnamon in another bowl. Sift half of the dry ingredients over the mixture and fold it ten times.

Add milk and fold it ten times. Sift the remaining dry ingredients into it and fold until you don’t see almost any flour left.

Add rum and fold until smooth. Add the raisins and dried berries. Fold roughly several times.

Put in the cake pan, flatten it, lower the oven to 180℃ / 356 F and bake for 52 minutes.

Remove it from the oven, and immediately drop the pan lightly onto your work surface to prevent the cake from shrinking. Let it cool for 20 minutes, leaving it in the pan.
Make syrup. Stir well sugar and boiling water to dissolve the sugar. Add rum and stir.

20 minutes later, remove the cake from the pan. Cut off the top a little to flatten.

Place the cake on plastic wrap and brush half of the syrup on top and sides. Set aside the remaining syrup because it will be used later. Double-wrap it with plastic wrap and let it sit at room temperature for 3 hours.

[Assenbling]
Add granulated sugar to whipping cream and use an electric hand mixer to beat until soft peaks form while cooling with ice water.
Slice the cake in half and brush each cut face with the remaining syrup. (You don't have to use up the syrup.)

Spread the cream over the 1st layer, and top it with rum raisins. Add the second layer, spread the cream over, and top with rum raisins and mint.

[Note]
You can cut it cleanly if you chill the cake in a fridge for 30 mins to harden the cream. Thank you!