In a large pan over medium heat, melt butter.
Sauté shallot and garlic in butter with a pinch of salt until soft and fragrant, a few minutes. Careful not to burn!
Pour milk into a microwave-safe bowl and microwave for 2 minutes.
As soon as you press 'start' on microwave, add in flour to shallot mixture and whisk continuously for 2 minutes. When the microwave goes off you know your whisking time is up!
Pour in warm milk over flour mixture and whisk well until all is incorporated.
Add in parmesan, lemon zest, and sage and give it another twirl.
Cook, whisking every-so-often, until sauce starts to thicken, about 10 minutes.
Taste and season with salt and pepper.
For a really good time, serve with my SPINACH RICOTTA GNOCCHI!