Creating Blackcurrant Mousse Cake can be an enjoyable journey. Follow these steps for a delightful outcome:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour an 8-inch round cake pan.

2. Mix Dry Ingredients: In a bowl, sift together flour, cocoa powder, sugar, baking powder, and salt.

3. Combine Wet Ingredients: In another bowl, whisk together eggs, milk, and vegetable oil until well combined.

4. Combine Mixtures: Gradually add the wet ingredients to the dry ingredients. Stir until smooth and no lumps remain.

5. Bake the Cake: Pour the batter evenly into the prepared cake pan. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.

6. Cool: Remove the cake from the oven and let it cool in the pan for 10 minutes. Then transfer it to a wire rack to cool completely.

7. Prepare the Mousse: In a saucepan, heat the blackcurrant puree over medium heat. Stir in sugar and adjust sweetness as needed.

8. Dissolve Gelatin (Optional): If using gelatin, dissolve it in a bit of warm water and stir it into the blackcurrant mixture. Remove from heat and let it cool slightly.

9. Whip the Cream: In a separate bowl, whip the heavy cream until soft peaks form. Be careful not to over-whip.

10. Combine Mousse: Gently fold the blackcurrant mixture into the whipped cream. Ensure it’s well combined but maintain the airy texture.

11. Assemble the Cake: Once the cake is completely cooled, place it back into the cake pan (you may want to line the sides with parchment paper for easier removal). Pour the mousse over the cake, spreading it evenly.

12. Chill: Cover and refrigerate the cake for 2-4 hours or overnight, until the mousse is fully set.

13. Unmold: Carefully remove the mousse cake from the pan. Place it on a serving plate.

14. Garnish: Decorate with fresh blackcurrants and mint leaves before serving.

By following these steps, you will create a stunning Blackcurrant Mousse Cake that will impress everyone at your gathering!