In two batches, transfer the mixture to a pre-chilled ice cream maker and churn into ice cream. When the ice cream is just about set up, soften ¼ cup of the remaining peanut butter in a saucepan or microwave just until it is thin and pourable. Let it cool for a few minutes. Turn the first batch of ice cream out into a container and drizzle with half the peanut butter. Use a knife or spatula to swirl the peanut butter into the ice cream. Hold the ice cream in the freezer and repeat with the second batch of ice cream. Freeze overnight for the best scooping texture.