Makes about 1 ½ cups of praline paste. 

260 g (2 cups) shelled pistachios

¼ teaspoon baking soda

150 g (¾ cup) sugar

30 g (1 Tablespoon) light corn syrup

50 g (about ¼ cup) water

½ teaspoon fine sea salt

2 teaspoons neutral-flavored oil, like sunflower oil

Heat the oven to 350F with a rack in the middle. Put the pistachios on a large, rimmed baking sheet and roast for 6 to 8 minutes, until they smell toasty. Watch the nuts carefully so they don't burn. Once roasted, put the pistachios on a plate or into a bowl to cool completely. 

Before you make the caramel, have a parchment-lined baking sheet nearby, and set the roasted pistachios and the ¼ teaspoon baking soda near the stove. In a 3-quart stainless steel saucepan, combine the sugar, corn syrup, salt, and water. Stir gently with a fork to mix. Turn to high heat and cover. Once it has boiled, keep the lid on for 1 minute, this helps wash any sugar crystals down the side of the pan. Remove the lid and boil until the sugar mixture starts to show a hint of golden color, then reduce heat to low and continue to cook until it has a medium amber color. Immediately add the pistachios and the baking soda and use a heatproof silicone spatula to combine. It will foam up! Quickly scrape the foamy caramel-nut mixture onto the prepared baking sheet. Spread it into a one-nut thick layer and let cool completely.

Once the praline has cooled, break it into chunks and put in the bowl of a food processor. Add the 2 teaspoons oil and process the mixture for 5 to 6 minutes. The praline will go through stages: from dusty, to a big boulder, to a gritty stiff paste, to a smoother paste. The paste will not be perfectly smooth, but stop when it has the consistency of almond butter. If you process it too much the paste may split and become oily.

Put half of the praline paste into a piping bag or zip-top bag to make the brownies. Refrigerate the rest in a sealed container for up to a month.