For the crust:
Pumpkin pie meets cookie bars in these delectable treats.
Preheat your oven to 350° and set a rack in the middle position. Grease a 9-inch square baking pan with butter.
In a medium-size bowl, combine graham-cracker crumbs, ground pecans, and cinnamon. Remove ½ cup of the mixture and set aside (you'll use it later in the topping). Add melted butter to bowl and stir with a fork to combine. Press evenly into bottom of pan and bake until lightly toasted, 10-12 minutes.
For the filling:
While crust is baking, make the filling: Whisk together pumpkin purée, brown sugar, half-and-half, egg, spice, vanilla, and salt. Pour pumpkin mixture over hot crust and return the pan to the oven for 20 minutes.
For the topping:
Now make the topping: In a small bowl, stir together oats, brown sugar, melted butter, and reserved crumb mixture. Once bars have baked 20 minutes, generously sprinkle streusel topping over pumpkin mixture and return to the oven for 20 minutes longer.
Let bars cool 15 minutes; then slice into 9 portions and serve, either plain or topped with whipped cream or a scoop of vanilla ice cream. Store leftovers in the refrigerator.