Note 1: If you'd like to make your own pistachio paste for the frosting, spread about 100g raw pistachios (unpeeled) on a baking sheet. Preheat the oven to 350 F and toast for about 10 minutes. While still very hot, transfer to a food processor and blend until the nuts turn into a runny paste - this can take up to 20 minutes, depending on your food processor. Measure out what you need for the frosting; I have you roast and process a little more than you need because some of the paste will be lost in the scraping process.