Sift together flour, cocoa powder, 6 oz (about 1 1/2 cups) powdered sugar and kosher salt. Pour into work bowl of a food processor.
In a separate bowl, lightly beat eggs until combined, then beat in water and 1 tbsp oil. Turn on food processor and slowly pour in liquid mixture until a stiff dough forms. Add a little more water if needed to bring the dough together.
Knead by hand a few times until smooth. Wrap in plastic wrap and let rest at room temperature to allow the flour to fully hydrate, about 1 hour. Roll by hand or through a pasta machine; fettucine or linguini-size noodles are best.
Bring 4 qts of salted water to a boil. Add pasta and cook 3-4 minutes or until tender. Drain thoroughly, then toss in a bowl with remaining 1 tbsp vegetable oil. Sift remaining 3 oz (3/4 c) powdered sugar over the pasta and toss to coat. Taste and add more sugar if needed. Cover with plastic wrap and chill thoroughly.
Meanwhile, combine raspberries and salt in a blender and puree until smooth. Add powdered sugar until desired sweetness is achieved. Pass through a fine-mesh sieve or chinois to remove seeds.
To serve, pour coulis onto a plate. Pile 4 oz pasta in the center. Garnish with fresh raspberries and grated white chocolate.