Nah, more like Stalin. Mussolini was a socialist. Fascism grew from that branch of the tree, historically.

Quite the contrary - fascism arose in opposition to socialism. Fascist theory emphasized heirarchical society and elitism, and deeply opposed the egalitarian and internationalist aspects of socialism - particularly socialism's rejection of nationalism, which is one of the key pillars of fascism. Fascism embraced capitalism and private ownership of property; though it called for capitalist systems to be subject to and controlled by the state, it completely rejected the idea that the means of production should be held in common by the workers (a core economic tenet of socialism).

Which is not surprising - politically, fascism rose to prominence in reaction to and in opposition to the Bolshevik Revolution of 1917. As Mussolini rose to power, the earliest targets he and his supporters went after were the socialists, the communists, and the trade unions. Those were fascism's enemies, not its roots.