- With the rack in the middle position, preheat the oven to 350°F (180°C). Butter the sides of an 8-inch (20 cm) square pan and line the bottom with a strip of parchment paper, letting it hang over two sides.
- In a bowl, combine the flour, ground almonds, cocoa powder, baking soda, baking powder and salt.
- In another bowl, whisk the eggs, sugar, brown sugar and oil with an electric mixer. With the machine running on low speed, or with a wooden spoon, add the dry ingredients alternating with the buttermilk. Spread the batter out in the prepared pan and top with the raspberries.
- Bake for 30 to 35 minutes or until a toothpick inserted in the centre of the cake comes out clean. Let cool completely on a wire rack, about 2 hours. Unmould.
- Meanwhile, place the chocolate in a bowl.
- In a pot, bring the cream and rose water to a boil. Remove from the heat and pour over the chocolate. Let melt for 2 minutes without stirring. Whisk until smooth. Let cool for 1 hour at room temperature or until thickened but still spreadable.
- Using a spatula, spread the ganache over the top of the cake. Sprinkle with the almonds and rose petals. The cake will keep for 3 days, covered, at room temperature.
Rose water can be found in the baking aisle of most supermarkets. Edible dried rose petals are available in some gourmet food shops or health food stores.