1 cup butter, melted
6 tablespoons all-purpose flour
1 cup white sugar
2 cups milk
1 teaspoon vanilla extract
1 cup chopped pecans
1 cup unsalted butter, divided
1/4 teaspoon salt
1 clove garlic, minced
Beat butter, sugar, milk, vanilla extract, pecans and salt in large bowl until well blended. Stir into sherry sauce mixture. Cover and refrigerate for 1 hour. Heat vegetable and nonstick cooking spray in large skillet or Dutch oven over medium heat.
Stir mixture into sherry sauce mixture. Cover and simmer 1 1 inch thick until thickened. Heat macaroni, cheese and onion mixture over medium heat until just tender. Cover and refrigerate for 30 minutes.
Stir slivered almonds into pan mixture. Bring to a simmer and cook, stirring occasionally, for 2 minutes or until mixture thickens slightly. Remove from heat. Stir into mixture before serving.