25 cups all-purpose flour (spooned and leveled)
1 tsp baking soda
5 tsp cornstarch (essential secret for ultra-soft, chewy centers)
1/2 tsp fine sea salt
3/4 cup (1.5 sticks) unsalted butter, softened to room temperature
3/4 cup packed light brown sugar (for rich moisture and caramel notes)
1/2 cup granulated sugar
1 cup large whole egg + 1 egg yolk (room temperature, yolk adds richness)
2 tsp pure vanilla extract
5 cups semi-sweet chocolate chips (or dark chocolate chunks)