Boil generously salted water for bonnetti. Add pasta to water once brought to a boil and cook for 5 minutes, until al dente.
Meanwhile, melt butter in a saucepan, being careful not to burn.
Add flour, garlic powder, and salt to melted butter. Stir until almost brown.
Add milk to saucepan, stirring constantly.
Add Greek yogurt. Stir, and heat on medium-high heat for 5 or so minutes until mixture thickens.
Once mixture has thickened, reduce to low heat, and add cheese, allowing it to melt.
Once cheese mixture is melted, add cooked pasta.
Serve immediately and enjoy!