In a large saucepan, brown the garlic in the butter (this takes about 7 minutes).
While vigorously whisking, slowly add the flour.
Cook, stirring continually, for about 5 more minutes. (Move on to the next step if the flour begins to brown.)
Add the milk, cream, parmesan cheese, salt, and pepper.
Stirring constantly, bring to a simmer over medium heat. Cook until thickened (it took about 45 minutes for a quadruple batch).