Preheat oven to 350°F. Line an 8-inch square pan with aluminum foil leaving overhang and spray with cooking spray, or grease and flour the pan; set aside.

In a microwave-safe bowl, melt butter and chocolate together in 2 minutes, stirring halfway through. Let cool slightly.

Add eggs, sugar, vanilla, and egg yolk to the chocolate mixture; whisk vigorously until well combined.

Stir in pumpkin puree and mix until smooth.

Add flour and salt, stirring until just combined without overmixing.

Pour batter into prepared pan and spread evenly.

Sprinkle chocolate chips evenly on top. Bake for 35 to 40 minutes until set.

Allow brownies to cool on a wire rack for 2 hours before slicing. Store airtight at room temperature for up to 1 week.