Cream butter in a large bowl with a mixer until softened.

Add light brown sugar, 1/2 cup of white sugar, vanilla, and egg to the creamed butter.

Beat until the mixture is light and creamy.

In a separate bowl, sift together flour, baking powder, and salt.

Add the sifted dry ingredients to the wet ingredients and mix well to form a dough.

Chill the dough for 1-3 hours, or until firm enough to roll out.

While the dough is chilling, prepare the date filling.

In a saucepan, combine chopped dates, 1/4 cup of white sugar, and 1/4 cup of water.

Bring the mixture to a boil, stirring often.

Reduce heat to a simmer and cook for 5 minutes, continuing to stir.

Add chopped pecans to the date mixture.

Remove the date filling from the heat and let it cool completely.

Preheat oven to 375 degrees F (190 degrees C).

Divide the chilled dough in half.

On a lightly floured surface, roll each half into a 9x12 inch rectangle.

Spread each rectangle evenly with the cooled date filling.

Roll each rectangle tightly into a log.

Wrap each log in wax paper.

Freeze the logs overnight to firm up for slicing.

Slice the frozen logs into 1/8 inch thick cookies.

Place the sliced cookies on a lightly greased baking sheet.

Bake in the preheated oven for 10 minutes, or until golden brown around the edges.

Remove from oven and let cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.