Preheat the oven to 350 F. Spread the nuts on a small baking pan. Toast for about 7-9 minutes, until fragrant. Without letting them cool, transfer immediately to a food processor (or strong blender) and grind the nuts on high. First the nuts will turn into bits, then a powder. Keep processing until the powder turns into a runny paste, this can take up to 10 minutes depending on the strength of the food processor. Scrape the paste out and set aside to cool. This can be done ahead of time, store the pistachio paste in an airtight container in the fridge (it’ll keep for a week or two).

Preheat the oven to 350 F. Line an 8x8 or 9x9 square baking pan (metal) with parchment paper. I like to do two overlaying strips so they cover the whole pan.

Set the butter in a heatsafe bowl and partially melt it (microwave for about 60 seconds). Add the brown sugar and whisk. Heat the mixture again, for about 60 seconds, then whisk until you have a thick, glossy mix.

Whisk in the salt and vanilla. Pour in the pistachio paste and whisk well.

Add the eggs one at a time, whisking well after each one. Switch to a rubber spatula and stir in the flour. If the mix is hot, wait to add the chocolate chips until it has cooled. Fold in the chocolate.

Bake the blondies until golden on the edges and the middle has puffed up and cracked a bit, about 30 minutes (look for visual cues for doneness, ovens vary as do pan material/size). Let cool then slice and serve.