Kitchen sink cookie bars

Ingredients

• 227 g unsalted butter, at room temperature
• 2¼ cup (293 g) plain (all-purpose) flour
• 2 tsp (6 g) cornstarch
• 1½ tsp (4 g) baking powder
• ¾ tsp (3 g) kosher salt
• 1 cup (200 g) packed brown sugar
• ½ cup (100 g) granulated sugar
• 2 large eggs, room temperature
• 2 tsp (10 ml) vanilla extract
• 2 cups (500 ml) mix-ins, such as crushed mini pretzels, crumbled cookies, chopped chocolate bars, nuts, toffee bits or chocolate chips
• Flaky sea salt

Cooling time: about 30 minutes total.

Instructions

1. Heat oven to 170°C (325°F). Grease a 23 cm (9 inch) square baking pan with non-stick cooking spray and line it with a sling of parchment paper.
2. In a small pot set over medium heat, melt the butter. If desired, you can brown the butter by simmering the butter for 5 to 7 minutes, stirring frequently, until golden brown flecks appear. Whether using melted butter or brown butter, immediately transfer it to a large bowl and set aside to cool slightly.
3. Meanwhile, whisk together the flour, cornstarch, baking powder and salt and set aside.
4. When the butter has cooled slightly, beat in the sugars until well combined. Beat in the eggs, one at a time, and stir in the vanilla. Add the dry ingredients into the butter mixture and mix until almost combined. Scatter in most of the mix-ins and stir just until evenly distributed.
5. Spread the batter into the prepared baking pan and scatter over the remaining mix-ins as well as a pinch of flaky sea salt. Bake for 30 to 35 minutes or until the edges are golden brown and the middle is set. Allow the cookie bars to cool slightly in the pan before lifting out and slicing into 12 equal bars.

Note

The cookie bars will keep covered on the counter for up to 5 days.