Butter two 8" cake pans and line the bottoms with parchment. Preheat the oven to 350F.
1. Sift the flour, soda, baking powder, and salt together and set aside.
2. For rose powder, grind a handful of dried roses with a little sugar in a coffee or spice grinder or mortar and pestle until it is a fine powder.
3. Place chocolate, cocoa, and rose powder in a medium bowl.
4. Steep the dried roses in the boiling water for 5-7 minutes, then strain into the chocolate bowl. Whisk until combined and smooth; add rosewater.
5. In the bowl of a stand mixer with the paddle attachment, cream the butter and brown sugar, 2-3 minutes. Add eggs, one at a time, scraping sides down with a spatula in between. Mix until well combined. Add sour cream and vanilla and mix.
6. Add about 1/3 of flour mixture into butter mix and gently combine. While mixer is running, pour half of the chocolate mixture in. Repeat with flour, chocolate, and end with the last 1/3 of the flour mix.
7. Divide batter between the two prepared cake pans and smooth out. Bake until set and just done, about 30-38 minutes. Allow to cool completely.
Place chopped chocolate in a medium bowl. Scald the cream. Pour the scalded cream over the chocolate, let sit one minute, and then whisk to combine. Add rosewater and whisk in gently.
Whisk together cream, vanilla bean seeds, extract, and sugar until soft peaks form.
1. Layer cake with ganache and whipped cream in between the two layers.
2. Use remaining ganache to coat the outside of the cake in a thin, even layer. Chill for at least 20 minutes.
3. Frost lightly with the remaining whipped cream. Chill until ready to serve.
Best if allowed to sit at room temperature for about 20 minutes before serving.