Coat a 9-inch round cake pan with cooking spray. Line bottom of pan with parchment paper; coat with cooking spray. Dust with 2 teaspoons flour.
Reserve 5 walnuts. Place remaining walnuts, 6 dates, and clementines in food processor; process until ground.
Combine brown sugar, butter, and oil in a large bowl; beat with a mixer at medium speed until well blended. Beat in vanilla and egg.
Combine flour, baking soda, and salt. Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture; mix after each addition. Add nut mixture and chopped dates; beat at medium speed 3 minutes. Pour batter into prepared pan. Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan.
Combine powdered sugar and juice, stirring with a whisk until smooth. Drizzle glaze over warm cake; spread to coat top. Top with reserved 5 walnut halves. Cool cake on a wire rack 30 minutes.
Fabulous cake! Not too sweet, but wonderfully flavorful and moist. More dense than the typical American cake, this reminds me of a cake I've had in France. My 17 year-old daughter asked me to make this for her birthday cake, and during the holidays, when clementines are plentiful, I make it and bring to parties. It's always eaten up and I've been asked for the recipe many times. It looks gorgeous, too. Thanks so much for sharing this recipe.
Because my daughter is allergic to walnuts, I substituted almonds and used a bit of almond extract to compensate for the more subtle flavor of almond. The recipe held up, and was very tasty. It is also a healthy treat for the kids.
I liked the recipe just the way it was; it reminded me of a light and fluffy fruitcake that has only good fruit in it! Next time, I will do a better job grinding the clementines, though, to avoid big chunks of rind. I can't wait to have another slice, after the flavors have mellowed and blended on my counter overnight.
I really liked this cake a lot. It was moist and tasty. Loved the slightly bitter sweet taste of the clemintine rinds. I am going to play with some options when I make it again. Maybe toast the walnuts and use lemon juice for the frosting.