How to Make It
Cook the lentils in a medium saucepan of boiling water until tender, 12 to 15 minutes. Drain well.
Meanwhile, in a large skillet, toast the pistachios over moderate heat, stirring, until deep golden, 4 to 5 minutes. Let cool completely.
In a food processor, pulse the pistachios with the garlic until the nuts are finely chopped. With the machine on, slowly drizzle in the olive oil, then drizzle in the water and lemon juice and puree until smooth. Add the coriander and lentils and pulse until smooth. Season the dip with salt. Scrape the dip into a bowl, stir in the parsley and serve with pita bread.