Bittersweet Chocolate Revel Bars

Preheat oven to 350ºF.

For the bars:
Beat butter and brown sugar until well blended. Add soda, eggs and vanilla. Blend well. Add remaining flour and oats, mix until combined.

For the filling:
In a saucepan over low heat, warm chocolate pieces with butter and sweetened condensed milk until melted and smooth. Stir in vanilla.

To assemble the bars:
Press 2/3 of the bar mixture into an ungreased 15x10x1 inch pan. Bar mixture will be sticky; wet fingers as necessary. Spread chocolate layer on top. Dot remaining pieces of dough on top of chocolate.

Bake at 350ºF for about 25 minutes, or until tops are lightly browned. Cool and cut. Store in airtight container at room temperature.