Butter an 8-inch plain or fluted tube pan. In a bowl, mix hazelnut spread and whipping cream until smoothly blended.
Pour evenly into bottom of pan.
In a large bowl with a mixer, beat 10 tablespoons butter and the sugar until well blended.
Add eggs, 1 at a time, beating until fluffy after each addition.
Sift together flour, cocoa, baking powder, baking soda, and salt.
Add flour mixture and milk to butter mixture; stir to combine, then beat until well blended. Spoon evenly over hazelnut mixture in pan.
Bake in a 350 oven (325 in a convection oven) until cake begins to pull from pan sides and springs back when lightly pressed in the center, 50 to 60 minutes. Cool for 5 minutes in pan, then slip a thin-bladed knife between pan rim and cake. Invert a large plate over cake. Holding pan and plate together, invert again and shake gently to release cake onto plate.
Let stand 2 to 3 minutes, then lift off pan. Scoop any hazelnut mixture left in pan onto top of cake.