It is not that socialism does not employ democracy, but rather that it is different from liberal democracies. The only way it has ever been successfully implemented is through Lenin's praxis based on Marx's theory i.e. Leninism, which translates into a one party rule. This does not mean that there are no election process in the whole ladder of beaurocratic and politicians who form part of the State and so on, only that there is no fight between parties. A party should care about one thing primarily, and thatis the wellbeign of the national proletariat, if that is the role to fullfill then it is pointless to gamble on which one to choose, because we can take decisions based on science when micro or macro managing a nation, not doing whatever is best for PR, and we do not need two parties for that.

AFAIK the most significance different aproach would be Allende's Cybersyn, but it never occurred since the CIA murdered him so we cannot say it would have worked, and that only distributed decision making at a micro level while still holding a hierarchical structure.