Preheat the oven to 350° and line a baking sheet with parchment paper. In the bowl of a standing electric mixer fitted with the paddle, combine the flour, sugar, almond flour, cocoa powder and salt. Add the butter and beat at medium-low speed until the dry ingredients are evenly moistened. Press the mixture into 1/2-inch clumps and refrigerate until firm, about 15 minutes. Spread the clumps on the baking sheet and bake for about 15 minutes, until fragrant and firm. Let cool. Wipe out the mixer bowl.
Butter and flour two 9-by-5-inch loaf pans. In a medium bowl, whisk the flour, cocoa powder, baking powder, baking soda, salt and cinnamon. In the mixer bowl, combine the sugar with the eggs, oil, crème fraîche, ginger and vanilla seeds and beat at medium speed until smooth. Gradually beat in the dry ingredients at low speed, scraping down the side of the bowl occasionally. Beat in the carrots.
Scrape the batter into the pans and top with the crumble. Bake in the center of the oven for 1 hour and 30 minutes, until a toothpick inserted in the center of the cakes comes out clean; cover the cakes loosely with foil during the last 30 minutes of baking. Transfer the pans to a rack and cool for 1 hour.
Lightly wrap the top of each cake in a sheet of foil to prevent the crumble from dislodging. Top with a rack and invert the cakes; remove the pans. Turn the cakes right side up and let cool completely before serving.
Look for almond flour, made from whole blanched almonds, at kingarthurflour.com.