Does anyone know if I can use the Hersey's cocoa choclate cake recipe but substitute the cocoa with Valrhona?

I know that you can substitute baking chocolate for cocoa, maybe could be the same. I am not sure. May be this information can help you

chocolate (bittersweet or semi-sweet) - 1 ounce (30 grams)
1/2 ounce (15 grams) unsweetened chocolate plus 1 tablespoon (15 grams) granulated sugar

chocolate (unsweetened) - 1 ounce (30 grams)
3 tablespoons (20 grams) natural cocoa powder (not Dutch-processed) plus 1 tablespoon (14 grams) unsalted butter, shortening, or vegetable oil

cocoa powder, Dutch-Processed - 3 tablespoons (20 grams)
1 ounce (30 grams) unsweetened chocolate plus 1/8 teaspoon baking soda. Also reduce fat in recipe by 1 tablespoon.

cocoa powder, natural unsweetened - 1 ounce (30 grams) unsweetened chocolate. Also reduce fat in recipe by 1 tablespoon.

The Valrhona might be dutch processed, which means they process it with alkali to take the bitterness out. Hershey's cocoa is naturally processed so you usually have to use baking powder, which contains alkali, to counteract the bitterness. A recipe designed for a higher end, dutch processed cocoa will almost always use baking soda. Check out the one I posted called Q's Favorite Chocolate Cake. I think it has a very similar taste and texture to the Hershey's cake (which used to be my favorite) but it uses baking soda and it bakes really level. (Flat, no hump or sinkage in the middle). Good Luck!