2 ounces fine-quality bittersweet chocolate
2 1/4 cups whole milk
1/3 cup heavy cream
3/4 cup minus 2 tablespoons superfine granulated sugar
1 cup unsweetened cocoa powder
4 large egg yolks
1/2 cup peanut butter
Chop chocolate. In a heavy saucepan bring milk, cream, and about half of sugar just to a simmer. Remove pan from heat and add cocoa powder and chocolate, whisking until chocolate is melted and mixture is smooth.
In a bowl with an electric mixer beat yolks and remaining sugar until thick and pale. Add hot chocolate mixture in a slow stream, whisking, and pour into saucepan. Cook custard over moderately low heat, stirring constantly, until it begins to thicken. Be careful not to boil the custard. Pour custard through a sieve into a bowl. Cover with plastic wrap and refrigerate until fully chilled 4 hrs-overnight).
Freeze custard in an ice cream maker. When almost done, drop teaspoons of peanut butter into ice cream maker. Transfer to an airtight container and put in freezer to harden, 1 to 3 hours. Serve with bananas and or whipped cream.