In a large bowl, combine the shredded coconut, chopped pecans, and quick oats. Toss and set aside.

Place a medium saucepan over medium heat and melt the butter.

Add the brown sugar, sweetened condensed milk, salt, and cinnamon (if using). Stir continuously.

When the mixture comes to a gentle boil, lower the heat and simmer for 2–3 minutes, stirring until the sugar dissolves and the mixture looks glossy.

Remove the pan from the heat and stir in the vanilla extract.

Immediately pour the hot syrup over the dry mixture. Stir briskly until everything is well coated.

Use a spoon or cookie scoop to drop portions onto a parchment-lined baking sheet. Press each mound lightly to shape a cookie.

Let the cookies cool at room temperature for 20–30 minutes, or chill in the refrigerator for 10–15 minutes until firm.