Step 1

Cook the filling: Combine the dates, water, vanilla, and salt in a small saucepan. Bring to a simmer over medium heat and cook until thickened, about 5 minutes.

Step 2

Cool the filling: Remove from the heat. Cool the filling for at least 30 minutes before making the crust.

Step 3

Prepare the pan and heat the oven: Arrange a rack in the middle of the oven and heat to 350°F. Coat an 8-inch square baking pan with cooking spray and set aside.

Step 4

Make oat flour: Process 1 cup of the oats in a coffee grinder, blender, or food processor until it resembles flour, about 3 minutes.

Step 5

Make the oat crust: Combine the oat flour, remaining 1 cup of coats, and brown sugar in a medium bowl. Add the butter and work into a crumbly mixture by beating with a sturdy spoon or spatula. Measure off 3/4 cup of this mixture and set aside.

Step 6

Pack in the crust: Pour the remaining crust mixture into the prepared baking pan. Tightly press the crust mixture into the pan.

Step 7

Add the filling: Spread the cooled date filling into the crust.

Step 8

Top with remaining crust mixture: Crumble and sprinkle the reserved 3/4 cup crust mixture over the filling.

Step 9

Bake: Bake until the crust is golden-brown and the filling is beginning to brown around the edges, 30 to 35 minutes.

Step 10

Cool and slice: Remove the bars from the oven to a cooling rack and cool for 1 hour before slicing into 12 bars.