1 For the cake batter, toast the ground and chopped walnuts in a dry pan until golden and allow to cool on a plate.
2 Grease the bottom of the springform pan. Preheat the oven to 180°C (approximately 350°F).
3 Melt the butter in a mixing bowl and stir until smooth with a hand mixer. Gradually add the honey and eggs, while stirring. Mix in the whole-wheat flour, baking powder, cocoa, and rum at a medium speed. Fold in the toasted walnuts. Spread the batter into the springform pan smoothly and bake for about 40 minutes until done (check with a toothpick).
4 Remove the cake from the oven, allow to cool in the mold, then remove and cut in half horizontally.
5 For the orange cream, soak the gelatin in cold water. Peel the orange and squeeze the juice. Warm the juice and liquor in a saucepan, drain the gelatin and dissolve in the mixture. Mix the cream cheese with the powdered sugar until smooth and stir 2-3 tablespoons into the dissolved gelatin. Add the gelatin mixture to remaining cream cheese and fold in the whipped cream. Spread about 1/3 of the cream on the cake base, place the second layer on top and coat the entire cake with the remaining cream cheese mixture. Refrigerate for around 2 hours.
6 Garnish the cake with orange zest and walnuts and serve slices.