With a mixer, beat heavy whipping cream until thick.
Pour in sweetened condensed milk and vanilla, then fold in until smooth.
Next, pour half the ice cream into a freezer safe container. Swirl in half of the peanut butter with a spoon or a knife. Repeat with another layer and the remaining peanut butter.
Freeze for 5–6 hours or overnight.
When it is time to serve, remove from freezer and let sit on the counter to soften for 5–10 minutes before serving.