Mix all the ingredients in a stand mixer bowl and knead for 10 minutes, until a smooth dough is formed. Cover the bowl and let the dough rise until doubled in size, about 1-2 hours, then refrigerate for two hours.
Dust your work surface with flour and roll out the dough into a ½" layer. Cut out triangles as shown in the video and roll each one inwards, like a croissant shape.
Place each cronut on a parchment paper square and let them rise for 30 minutes.
Fill half of a deep pot with frying oil and heat it up on medium-high. Deep fry the cronuts until they golden all around and let them cool off on a rack.
Pastry cream:
Heat up the milk, egg yolks, sugar, cornstarch and vanilla paste in a small pot and whisk until the texture thickens and becomes creamy.
Remove from the heat, add the butter and pistachio paste and whisk until well combined. Transfer to a container covered with plastic wrap and place in the fridge for two hours.
Assembly:
Cut each cronut open horizontally, fill with 1 heaping teaspoon of the pistachio pastry cream and sprinkle a little powdered sugar on top.