In a medium saucepan toast the pistachios over medium heat for about 5 minutes until they smell fragrant. Reduce the heat to low. Add the half and half. Heat until bubbles form around the edge of the pan. Remove from the heat, cover and let steep for 30 minutes.
(If you want to temper the yolks you can do that now by removing the nuts (set aside for later) and then whisking the yolks into the warm half and half. Reheat over low until it thickens enough to coat the back of a spoon. Then proceed with the rest of the recipe.)
In a blender combine the 1 cup pistachios, half and half, egg yolks, almond milk, heavy cream, and sweetener. Blend until smooth. Refrigerate until cold. Freeze in an ice cream machine according to the manufacturer's instructions.
If desired you can add ½ cup toasted pistachios during the last few minutes of mixing or just sprinkle them on top when serving.