Lay salmon on a foil lined baking sheet, skin down. Spread a thin layer of mayo across the top. Process pistachios in a food processor until finely chopped and press into even layer on top of salmon. Use an olive oil mister or drizzle olive oil over top of salmon. If using unsalted pistachios, option to sprinkle a pinch of salt & pepper over each for taste.
Add noodles to boiling water and cook until al dente, every noodle is different so I encourage you to use package instructions or taste test until desired texture! Drain noodles when they are done and set aside in your strainer.
Add salmon to oven and cook 6-8 minutes until pistachios start to golden and toast on top. Remove from oven when done and set aside.
While noodles boil and salmon bakes start your sauce. In a small saucepan add minced garlic and butter over medium heat until melted. As soon as melted add in your flour and quickly whisk until an even paste forms. Pour in your milk and turn heat to high, whisking until fully combined. As soon as you start to boil, add in your parmesan cheese and turn heat to low, stirring in and allowing sauce to thicken. I used an immersion blender to add in basil, pinch of salt & pepper (add as much as you want of these 3 ingredients to taste). You could also just finely chop basil and stir in at end if you don't want to blend.
Add cooked noodles back to their pot and pour in sauce slowly, stirring until noodles are evenly coated. Layer noodles in a bowl and top with salmon. Slice salmon if desired.
Notes
If cooking for just two like I was, you will have extra sauce.. you can store in fridge for a few days to use again. It will not freeze well. Easily increase the servings to four by just adding extra salmon & pistachios and more noodles.
You can use regular grated parmesan if you have on hand. I prefer parmigiano reggiano as it is what I use for pesto which inspired this dish, but regular parmesan would be great!
The amount of spaghetti you make is really personal choice, we were starving while making this one up so made a full 8 oz for two, which is a very filling serving. Use a little less than 8 oz for a more moderate portion.