Preheat the oven to 350˚. In a small bowl, mix the 2 tablespoons water and the corn starch. Set aside. Bring one cup of water and 1/2 cup of brown sugar to a low boil in a medium saucepan. Reduce the heat to medium. Add the dates and the corn starch mixture. Keep simmering until the mixture thickens, about 6-8 minutes. Turn off the heat and add the vanilla extract. Mix well.
Beat the butter into a cream. Add 1 cup of brown sugar, the flour, the baking soda, the salt, and the oatmeal, and mix well. Spread half of the mixture at the bottom of an 8×8 baking dish lined with parchment paper. Compact well. Add the date mixture on top, and top with the rest of the oatmeal mixture (do not press down on the top as you want it to look like a fluffy crumble). Place in the oven for 25-30 minutes, or until golden on top. Let cool on a rack for about an hour. Cut in squares and eat them all! Bon appétit!