For the Filling:
2 1/2 c. strawberries, fresh or frozen
1/4 c. water
1/2 c. sugar
3 Tbsp corn starch + 1/4 c. cold water
For the Cookie Dough:
1/2 c. butter
1/2 c. brown sugar
1 tsp. vanilla extract
1 3/4 c. + 2 Tbsp flour
1/2 tsp. baking powder
To make the filling: The filling will need to cool down before being used, so make sure you make the filling first.
In a small pot, add the strawberries, water, and sugar. Bring to a simmer, then simmer for 10-15 minutes.You will need to stir regularly and break up the strawberries with a spoon as they cook.
Dissolve the corn starch in the cold water. Add slowly to the boiling strawberry mixture. Stir constantly. Cook for another few minutes until the mixture thickens and becomes the consistency of pie filling. Make sure you're stirring constantly.
Remove from heat and transfer to a glass bowl to cool. Cool for at least 30 minutes, stirring it every now and then before using it in the cookie bars.
To make the cookie dough: Preheat the oven to 350 F.
Cream the butter and sugar together.
Beat in the egg and vanilla.
In a small bowl, mix together the flour and baking powder, then fold into the creamed mixture until a dough forms.
Divide the dough into two equal parts.
Line an 8x8 inch baking pan with plastic wrap and press one half of the dough evenly into the bottom of the lined pan. Lift the flattened dough out of the pan, still keeping it on the plastic wrap, and chill in the fridge until you are ready to use it.
Lightly grease the baking pan and line it with parchment paper.
Press the other half of the dough evenly into the bottom of the prepared pan.
Spread the strawberry filling evenly over the base layer.
Take the dough square from the fridge and peel back part of the plastic wrap so you can flip it onto the filling. Then peel the rest of the plastic wrap off. Press down lightly on the dough.
Bake for 25-35 minutes, until lightly golden on top.
Cool completely before cutting into bars.
Here's a link to the recipe I used: http://www.rockrecipes.com/raspberry-filled-cookie-bars/