Joy the Baker has a good homemade pistachio pudding. The recipe calls for 2 cups whole milk, 2 large egg yolks, 1/3 cup granulated sugar, 2 tablespoons cornstarch, and a pinch of salt, as well as 1 teaspoon vanilla extract, 2 tablespoons unsalted butter and 1/2 cup chopped pistachio nuts.
The first step is to make a pistachio paste. To make, add 1/2 cup of salted pistachio nuts to a food processor, and pulse until chopped into tiny pieces. Add 2 tablespoons of water and 1/3 cup of granulated sugar, and blend to a smooth consistency.
To make pistachio pudding, add the paste to a medium-sized saucepan. Pour in the milk, and whisk well over medium heat. Continue to heat the mixture until it starts to steam.
While the milk is still heating, in a separate large bowl, whisk together egg yolks, cornstarch, granulated sugar and a pinch of salt. Continue whisking until it is smooth and starts to thicken. Add 1/2 of a cup of hot and steaming pistachio milk into the egg mixture, and whisk. Pour in another 1/2 cup of pistachio milk, and whisk to combine. Pour the mixture back into the pan, and continue to cook over medium heat.
Continue whisking constantly while heating, and bring to a boil for one minute and remove from heat. Add in vanilla extract and butter, and stir until butter has melted. Strain the mixture through a fine mesh, and spoon into small ramekins. Chill for at least 4 hours.