In a food processor, pulse the pistachios until they are finely chopped. Add the flour, sugar, and salt and pulse to combine. Add the butter and pulse until the dough starts to come together and becomes crumbly.
Dump the dough into an 8x8 square baking pan and press gently to even out. Prick holes all over the dough with a fork.
Bake until golden, about 45 minutes. When there is 5 minutes left of baking, warm the honey briefly and then brush all over the top of the shortbread, then return pan to the oven.
Let cool slightly, then slice and carefully remove slices to a wire rack to cool completely. Store in an airtight container.