In a medium saucepan, melt butter on medium heat. Add shallots, stir, and allow to keep boiling until a fragrant, nutty smell starts to arise. Immediately lower heat and sift in flour, whisking vigorously to remove any flour clumps that would try and form. When mixture is smooth, add roasted garlic, then milk and cream and salt and pepper. Whisk and turn heat back up to medium. Whisk continually as cream mixture begins to thicken. As soon as the sauce coats the back of a spoon, it’s ready for the final addition of cheese. Add and stir until creamy and smooth. As a final step, blend the sauce in a blender to ensure it’s whipped and creamy. Store in an airtight jar in the fridge for up to 5-7 days.