In the beginning there was no Brahma, no Siva, only Krishna. The cosmic manifestation is from Mahat Tattva, and before the Maha Tattva there is Narayana. Sankaracarya is a Lord Siva worshipper and an incarnation of Lord Siva, and he admits that Narayana is the master, and Narayana is the Supreme. narayanah paro 'vyaktat. This is the best authority. What more evidence you want? This is in his Sanka Bhasya on Bhagavad-gita. This is not even the statement of the Puranas but of Sankaracarya's own writings. How can you deny if the incarnation of Lord Siva says that Krishna is Supreme?
Letter to His Holiness Satsvarupa das Goswami, 3 November, 1974