1/2 cup (1 stick) unsalted butter, softened
1/2 cup packed light brown sugar
1/4 cup granulated sugar
1 teaspoon vanilla extract
1/2 cup canned pumpkin
11/2 cups all-purpose flour
1/2 teaspoon table salt
1/2 teaspoon pumpkin pie spice
1/4 teaspoon baking soda
1 1/2 cup coarsely chopped semisweet chocolate chunks or chips -divided
1 1/2 cup toffee pieces -divided
Vanilla ice cream, for serving
Preheat oven to 350°F. Coat a 10-inch cast-iron skillet (or cake pan) with nonstick spray. Using an electric mixer, beat butter, brown sugar, granulated sugar until well mixed. Add egg and vanilla in a medium bowl on medium-high speed until light and fluffy, 3 to 5 minutes. Beat in pumpkin until evenly incorporated.
Whisk together flour, salt, pumpkin pie spice, and baking soda in a bowl; add to butter mixture and beat on low speed until just combined, about 1 minute. Beat in 1 cup each of the chocolate and toffee pieces.
Spread batter in prepared skillet and smooth top with spatula. Sprinkle remaining 1/2 cup each chocolate and toffee over top. Bake until set in the middle and browned around the edge, 25 minutes or until just set in the middle. Cool in pan 20 minutes.