From Longman Dictionary of Contemporary Englishplain chocolateˌplain ˈchocolate noun [uncountable] British EnglishDF chocolate made without milk and with very little sugar syn dark chocolate
Examples from the Corpusplain chocolate• Cool. 4 Melt the white and plain chocolate in separate bowls over hot water.• Mix cheeses. melt plain chocolate in a bowl over a pan of simmering water.• Spread white chocolate layer over plain chocolate in tin, then add remaining chocolate layer.• Chill until set. 3 Melt the remaining plain chocolate and the white chocolate in separate bowls over hot water.• Melt the remaining plain chocolate in a pan with the cream.• Why couldn't those concerned realize that plain chocolate combined best with ice-cream?