Meanwhile, in a medium, heavy-bottom saucepan, whisk together egg yolks, the remaining 1 cup sugar, the milk and 1/4 teaspoon of the sea salt. Cook, stirring constantly, over medium heat until custard thickens and begins to bubble. Remove from heat; add gelatin mixture. Whisk until gelatin has dissolved and mixture is smooth. Whisk in peanut butter, vanilla and the remaining 1/8 teaspoon sea salt. Cool to room temperature.