Fudgy Pinwheel Cookies

This is a recipe from Taste of Home magazine's Christmas Cookies & Candies issue. I'm really looking forward to making Christmas cookies. One year I made peppermint pinwheel cookies which looked beautiful, but weren't totally delicious because peppermint is not my favorite flavor. These look slightly less pretty but more yummy:

1/2 cup butter, softened
1/2 cup packed brown sugar
1 egg yolk
1/2 tsp vanilla extract
1 cup all-purpose flour
1/2 tsp salt
1/4 tsp baking powder

Filling:
1 cup (6 oz) semisweet chocolate chips
1 tablespoon shortening
1 cup finely chopped walnuts
1/3 cup sweetened condensed milk
1 tsp vanilla extract

In a large mixing bowl, cream butter and brown sugar until light and fluffy. Beat in egg yolk and vanilla. Combine the flour, salt and baking powder; gradually add to creamed mixture and mix well.

Roll out dough into a 12 inch by 10 inch rectangle between 2 sheets of waxed paper.; transfer to a baking sheet. Refrigerate for 30 minutes.

Melt chocolate chips and shortening. Stir in the walnuts, milk and vanilla. Remove waxed paper from dough; spread with filling. Tightly roll up jelly-roll style, starting with the long side. Wrap in plastic wrap; refrigerate for 2 hours or until firm.

Unwrap and cut into 1/4 inch slices. Place 2 inches apart on lightly greased baking sheets. Bake at 375 degrees for 8-10 minutes or until set. Remove to wire racks. Store in an airtight container.

Makes about 30 cookies.