Heat oven to 350ºF (177ºC).
Arrange 1¾ cups pistachios on a quarter sheet pan (13x9-inch) and roast until lightly golden brown and fragrant, 8–10 minutes.
Remove from oven and let cool 10 minutes. Measure out and set aside 2 tablespoons roasted pistachios.
Add remaining (slightly warm) nuts to a food processor and blend until it goes from sandy to nut butter texture (it will likely blend into a large ball), about 3 minutes.
Add reserved 2 tablespoons pistachios, 2 tablespoons oil, ½ teaspoon salt and ¼ teaspoon almond extract; process until smooth with a few pistachio chunks, about 10 seconds. Wipe out quarter sheet pan (used to roast nuts) and grease with oil; set aside.
In a saucepan, heat ¾ cup sugar and ¾ cup corn syrup over medium, stirring occasionally, just until bubbles start to form around edges of pan. Add pistachio butter, remove from heat and stir to combine. Add 4 ½ cups cereal and, using a rubber spatula, work quickly to mix together.
Transfer to greased quarter sheet pan and press into an even layer (but don’t pack it down!). Set aside to cool.
In a microwave-safe bowl, combine ¾ cup semi-sweet chocolate and ½ cup dark chocolate chips. Microwave in 30 second increments on 50% power, stirring after each increment, until smooth. Spread onto scotcharoo and chill in fridge 30 minutes.
Cut as desired and enjoy. These are best served at room temperature, but I recommend storing them in an airtight container in the fridge. Let them come to room temperature before enjoying.