Preheat Oven:
Preheat oven to 350°F (175°C). Grease or line a 9x13-inch baking pan with parchment paper.
Prepare the Date Filling:
In a small saucepan, combine chopped dates, water, and brown sugar. Cook over medium heat, stirring occasionally, until the dates are soft and the mixture thickens (about 5–7 minutes). Stir in vanilla extract. Set aside to cool slightly.
Make the Crust & Topping:
In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs and vanilla extract. In another bowl, whisk together flour, baking powder, salt, oats, and nuts (if using). Gradually mix dry ingredients into the wet mixture until crumbly but cohesive.
Assemble the Bars:
Press about 2/3 of the oat mixture into the prepared pan to form an even crust. Spread the date filling over the crust. Sprinkle the remaining oat mixture evenly on top.
Bake:
Bake for 35–40 minutes, or until the top is golden brown. Allow bars to cool completely in the pan on a wire rack.
Serve:
Lift bars from pan using parchment paper, if used, and cut into squares or rectangles.