Over a low heat, warm the milk in a small pan with the sugar and vanilla. Set aside to cool completely.
Gently beat the cooled milk into the peanut butter to blend well, then fold in the whipped cream.
Pour the mixture into a deep container and cover with clingfilm or greaseproof paper, then close with a well-fitting lid.
Freeze for one hour in a really cold freezer. Using a fork, scrape the frozen ice cream from the edges then whisk the mixture to a smooth, even texture. Cover the container again and return to the freezer for another hour.
Repeat this process once or twice more at least, until the ice cream is smooth and nearly evenly frozen. When the ice cream is almost firm, add the extra nuts.
Freeze for 15 minutes before serving. This ice cream can be stored in the freezer for up to three months but take it out 15 minutes before serving to soften.
1 small pan
1 deep container
Ice cream maker (optional)
Clingfilm or greaseproof paper