Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone baking mats.
In a medium bowl, whisk together the flour, baking soda, salt, and cinnamon (if using). Set aside.
n a large bowl, using an electric mixer, beat the softened butter, granulated sugar, and brown sugar together until light and fluffy (about 2-3 minutes).
Beat in the egg and vanilla extract until well combined. Scrape down the sides of the bowl as needed.
Add the mashed ripe bananas and mix on low speed until just combined. Don't overmix. The batter might look a little curdled at this point – that's okay.
Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined. Be careful not to overmix.
Gently fold in the chocolate chips and chopped nuts (if using) with a spatula.
For thicker cookies and more developed flavor, cover the bowl and chill the dough in the refrigerator for at least 30 minutes, or up to overnight. (If chilling for longer than an hour, you may need to let it sit at room temperature for a few minutes to soften slightly before scooping.)
Drop rounded tablespoons of dough (or use a medium cookie scoop) onto the prepared baking sheets, about 2 inches apart.
Bake for 12-15 minutes, or until the edges are golden brown and the centers are set.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.