Preheat the oven to 350°F (180°C) and line a baking sheet with parchment paper. Set aside.
In a medium bowl, whisk together the flour, baking soda and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or with a handheld electric mixer), cream the butter and sugar together on medium speed until light and fluffy, about 3 minutes.
Add in the mashed banana, followed by the egg and vanilla extract.
Fold in the flour mixture and then finally stir in the chocolate chips.
Drop heaping tablespoon-sized mounds about 3-inches (7½ cm) apart on the baking sheet and bake for about 13 minutes, until the edges are brown and the center is set. Let cool on a wire rack while you bake off the remaining dough.
Store cooled cookies in an airtight container at room temperature for up to 2 days.