Preheat the oven to 350°F. Line a 9" x 9" inch pan with parchment paper and set aside. (8” x 8” pan works just fine. The bars will be slightly taller.)
For the crust and topping. In a large mixing bowl, add flour, oats, sugar, maple syrup, cinnamon, salt, and melted butter. Stir until well combined.
Firmly press ¾ of the mixture into the bottom of the pan. Set aside the remaining mixture in the fridge.
Place in the oven and bake for about 20 minutes, or until the crust is slightly golden. Then let cool for about 10 minutes.
You can make the filling either while the crust is baking or while it is cooling.
For the filling. In a large mixing bowl, add pumpkin puree, eggs, milk, both sugars, vanilla, spices, and salt. Stir until combined.
Pour filling on top of the cooled crust and return to the oven to bake for 15 minutes. Remove from the oven.
Remove the remaining topping from the fridge and pinch off pieces, about the size of a cherry, scatter over the top of the filling. Don't worry about the pieces sinking into the filling!
Return the pan to the oven and continue to bake for 35-40 minutes or until the filling is firm/set and the topping is a beautifully golden.
Leave the bars in the pan until cool. About 1 hour.