Peel a small onion and grate with a cheese grater to get 1 teaspoon of very finely grated onion. It will almost be pureed. This texture is important so it mixes well with the cream cheese without creating any chunks of onion.
In a small mixing bowl, combine the cream cheese, grated onion, garlic powder, and 1 teaspoon of the Worcestershire sauce. Scoop onto a sheet of plastic wrap and form into a disk. Wrap tightly with the plastic wrap and place in the refrigerator. Chill for 2 hours or over night to allow the flavors to meld. After chilling the cream cheese, unwrap it and place on a serving plate.
In a medium saucepan, melt the butter over medium heat, then add the brown sugar, brown mustard, and the remaining 1 teaspoon of Worcestershire sauce. Cook over medium heat, stirring often, until the sugar is melted and the sauce is smooth.
Add the pecans to the sauce and stir to coat.
Pour the pecan mixture over the cream cheese disk and serve immediately with crackers.