In a medium bowl, melt butter in the microwave or in a double boiler; stir in vanilla and set aside to cool.
In a large bowl, whisk together the flour and sugar. Stir in the butter mixture; stir in the toffee bits and chopped pecans (mixture will be crumbly). Shape into 1-inch balls and place 2 inches apart on ungreased baking sheets. Flatten slightly.
Bake at 375° for 12 minutes, or until edges begin to brown.