For the brownies: Preheat the oven to 325 degrees F and grease and flour a 9-by-13-inch baking dish.
Place the chocolate and butter in the top of a double boiler and melt over low heat. Let cool slightly. Beat the eggs and sugar together until thick and pale yellow in color. Add the cooled chocolate mixture and stir well to combine. Sift in the flour, fennel powder, cardamom seeds, fennel seeds, smoked paprika and salt, and stir well until completely combined. Pour into the prepared pan and bake until an inserted toothpick comes out clean, about 30 minutes. Let cool.
For the ganache: Chop the white chocolate and place into a heatproof bowl. Place the cream and ground cardamom in a small saucepan over medium heat. Bring to a boil. Pour the hot cream over the white chocolate. Let sit for 30 seconds, and then stir until it is very smooth. Pour the ganache over the brownies and let cool completely until the ganache is set. Cut into squares.