Preheat the oven to 190°C (375°F). Line two baking sheets with parchment paper or lightly grease them and set aside.

In a large mixing bowl, cream the softened unsalted butter with the granulated sugar and light brown sugar until light and slightly fluffy, about 2 to 3 minutes using a hand mixer or stand mixer on medium speed. Scrape down the bowl once.

Beat in the large egg and vanilla extract until combined. Then stir in the mashed ripe bananas until the mixture is smooth and uniform. If you prefer a more banana-textured cookie, leave a few small lumps.

In a separate medium bowl whisk together the all‑purpose flour, baking soda, baking powder, ground cinnamon and fine salt until evenly distributed.

Add the dry ingredients to the wet ingredients and fold using a spatula or low speed on the mixer just until no streaks of flour remain. Do not overmix; overworking will make the cookies tough. If dough feels too slack, chill 10 minutes.

Fold in the semisweet or dark chocolate chips (and the chopped nuts, if using) until evenly distributed. Reserve a small handful to press on top of the dough mounds for presentation if desired.

Portion the dough into generous tablespoon-sized mounds (about 2 tablespoons per cookie for larger cookies) using a cookie scoop or two spoons, spacing them about 2 inches (5 cm) apart. Slightly flatten each mound and press a few extra chocolate chips and a banana slice on top of some cookies for the banana‑bread look.

Sprinkle a small pinch of coarse finishing salt or coarse sugar on top of selected cookies if you like a sweet-salty contrast or added crunch; alternatively sprinkle a little additional granulated sugar.

Bake one tray at a time on the middle rack of the preheated oven for 10 to 12 minutes, or until edges are golden and centers are set but still soft. Rotate the sheet halfway through baking for even browning. For slightly smaller cookies, reduce bake time by 1 to 2 minutes.

Remove the cookies from the oven and allow them to rest on the baking sheet for 3 to 5 minutes — this helps them finish setting without losing moisture — then transfer to a wire rack to cool completely or to preferred serving temperature.

If the dough feels sticky when scooping, chill it for 15 to 30 minutes; this will reduce spread and restore shape. Use the optional 1 tablespoon of vegetable oil or melted butter sparingly in the dough if you want slightly more pronounced browning; fold it in when adding the mashed banana.

Store cooled cookies in an airtight container at room temperature for up to 3 days, or freeze in a sealed bag for up to 3 months. Reheat briefly in a 160°C (325°F) oven for 5 to 8 minutes or in a microwave for 10 to 20 seconds to revive softness.

If you like a more banana-bread texture, swap 30 g (about 1/4 cup) of the all‑purpose flour for an equal amount of whole wheat flour and increase mashed banana by 25 g (about 1/8 cup). Adjusting flour this way will increase chew and density.