Step 1: Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
Step 2: In a medium bowl, whisk together 2 1/4 cups all-purpose flour, baking powder, baking soda, salt, cinnamon, nutmeg, ginger, and cloves. Set aside.
Step 3: In a large bowl, cream softened butter, 1 1/2 cups granulated sugar, and brown sugar until light and fluffy.
Step 4: Beat in eggs one at a time, then stir in pumpkin puree and 1 teaspoon vanilla extract until just combined.
Step 5: Gradually add dry ingredients to wet ingredients, mixing on low speed until just combined. Pour batter into the prepared pan and spread evenly.
Step 6: Bake for 25-30 minutes, or until a wooden skewer inserted into the center comes out clean. Cool completely on a wire rack.
Step 7: For the Chai Caramel, combine 1 cup granulated sugar and 1/4 cup water in a heavy-bottomed saucepan. Cook over medium-high heat, stirring until sugar dissolves, then stop stirring.
Step 8: Boil until the mixture turns a deep amber color (8-12 minutes). Carefully pour in warmed heavy cream, 4 tablespoons butter, and chai spice blend. Whisk continuously until smooth.
Step 9: Reduce heat to low and simmer for 5-7 minutes until slightly thickened. Remove from heat, stir in 1/2 teaspoon vanilla extract and pinch of salt. Let cool to room temperature.
Step 10: For the Cardamom Crumble, whisk 1 cup all-purpose flour, 1/2 cup granulated sugar, and ground cardamom in a medium bowl.
Step 11: Cut in cold, diced butter using your fingertips or a pastry blender until coarse crumbs form. Spread onto a parchment-lined baking sheet.
Step 12: Bake at 350°F (175°C) for 10-12 minutes, until golden brown. Let cool completely.
Step 13: Once bars are cool, pour cooled chai caramel over them, spreading evenly.
Step 14: Generously sprinkle cooled cardamom crumble over the caramel layer.
Step 15: Refrigerate for at least 30 minutes to set the caramel before cutting into squares and serving.