In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and cinnamon (if using). Set aside.
2 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 1/2 teaspoon fine sea salt, 1 teaspoon ground cinnamon
In a large mixing bowl, beat the softened butter, maple syrup, and brown sugar together with a hand mixer or stand mixer on medium speed for 2–3 minutes, until light and slightly fluffy.
1/2 cup unsalted butter, 1/2 cup pure maple syrup, 3/4 cup light brown sugar
Add the egg, vanilla extract, and maple extract to the bowl. Beat again until smooth and creamy, scraping down the sides as needed.
1 large egg, 2 teaspoons pure vanilla extract, 1 teaspoon maple extract
Add the dry ingredients to the wet mixture in two additions, mixing on low just until combined. Add the milk and mix briefly. The dough will be soft and slightly sticky.
2 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1/2 teaspoon baking powder, 1/2 teaspoon fine sea salt, 1 teaspoon ground cinnamon, 2 tablespoons milk
Cover the bowl and refrigerate the dough for at least 30 minutes and up to 24 hours. If chilled overnight, let sit at room temperature for 5–10 minutes before scooping.
When ready to bake, preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
Using a cookie scoop or tablespoon, portion the dough into about 1 1/2-tablespoon balls. Roll gently between your palms to smooth and place on the prepared baking sheets, spacing about 2 inches apart.
Bake one sheet at a time for 9–11 minutes, until the edges are set and lightly golden but the centers still look slightly soft. The cookies will continue to firm up as they cool.
Let the cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely before icing.
In a medium bowl, whisk together the powdered sugar, maple syrup, maple extract, and a small pinch of salt. The mixture will be thick at first.
1 1/2 cups powdered sugar, 3 tablespoons pure maple syrup, 1/2 teaspoon maple extract, salt
Whisk in milk or cream, a teaspoon at a time, until the icing is smooth and pourable but still thick enough to coat a spoon, like honey. If it becomes too thin, whisk in a bit more powdered sugar.
1 tablespoon milk or cream, 1 1/2 cups powdered sugar
Once the cookies are completely cool, spoon about 1–2 teaspoons of icing over each cookie or dip the tops into the icing, letting excess drip back into the bowl. Place cookies on a wire rack set over parchment to catch drips.
Allow the iced cookies to sit at room temperature for 30–45 minutes, or until the icing firms up and loses its shine. Then stack, store, or serve.