Bring a large pot of salted water to a boil. Add the pasta and cook according to the package instructions until al dente.
In a large saucepan, melt the unsalted butter over medium heat.
Once melted, add the all-purpose flour to the butter.
Stir continuously with a whisk or wooden spoon to combine the flour and butter, cooking for about 2-3 minutes until the mixture turns light golden brown. This forms your roux.
Gradually pour in the milk, whisking constantly to avoid lumps.
Cook the mixture, stirring frequently, until it thickens to a creamy consistency, about 5-7 minutes. Do not make the heat too high or you will risk breaking the sauce!
Reduce the heat to low and add the soy sauce. Stir in the freshly grated white cheddar cheese until fully melted and smooth.
Add the cooked pasta to the saucepan with the white cheddar béchamel sauce. Gently toss the noodles until they are evenly coated in the sauce.
Divide the mac among serving plates or bowls. Top each serving generously with chili crisp according to your taste preference. A little goes a long way. You can also add chili crisp to the entire batch and toss it in, then use it as a topping at the end as well. Garnish with finely chopped scallions and serve!
