1-First, preheat your oven to 350°F and grease an 8 by 8-inch baking dish. In a bowl, whisk together 1 1/4 cups all-purpose flour, 1 1/4 cups old-fashioned oats, 1/2 teaspoon salt, and 1/2 teaspoon baking soda for about 30 seconds. Then, add 1/2 cup granulated sugar and 1/2 cup packed light-brown sugar, mixing until smooth.

2-Next, stir in 3/4 cup melted butter and 1 teaspoon vanilla extract until the mixture is evenly moist. Press half of it into your prepared dish and bake for 15 minutes. While that’s baking, in another bowl, whisk together 1/4 cup granulated sugar, 1/4 cup packed light brown sugar, 1 teaspoon ground cinnamon, 1/2 teaspoon ground nutmeg, 1/4 teaspoon ground ginger, 1/8 teaspoon ground cloves, and 1/4 teaspoon salt.

3-Adding the Filling: Once mixed, add 1 large egg plus 1 large egg yolk, 1 teaspoon vanilla extract, and 1/2 teaspoon ground allspice, blending well. Stir in 1 1/4 cups canned pureed pumpkin and 1/3 cup evaporated milk or half and half. Pour this over the baked base and bake for another 15 minutes.

4-Finishing Touches: Sprinkle the remaining crumb mixture on top, breaking it into small bits. Adjust your oven rack higher and bake for 20 to 25 minutes more, until golden and slightly jiggly in the center. Let it cool for 1 hour at room temperature, then chill for another hour or serve warm. Cut into squares and enjoy, perhaps with whipped cream.