Spray a 9 inch quare baking pan with no-stick cooking spray. Heat oven to 350 degrees.
Combine dates with water in a saucepan and bring to a boil. Reduce heat and simmer until thickened, stirring frequently (a few minutes). Remove from heat, stir in vanilla and set aside.
In a medium bowl, combine oats, flour, sugar, baking soda and salt. Mix well with a pastry blender.
Melt butter in a saucepan and remove from heat. Immediately stir in sour cream, mixing until evenly blended. Drizzle over the top of oat mixture and blend with pastry blender.
Spread 2 cups of oat mixture in bottom of prepared pan and press firmly. Spread date filling on top. Combine nuts with remaining oat mixture using a pastry blender, then pat firmly and evenly onto filling.
Bake in center of oven for 20 minutes or until golden brown. Let cool. Cut into 25 squares.
