Combine flour, baking soda, cornstarch, salt, and spices.
In a stand mixer with paddle attachment (or hand mixer), beat the soft butter and sugars until creamy.
Add molasses, and beat until combined.
Then, add the egg and vanilla. Beat until smooth and creamy, about 2 minutes.
Gradually add the flour mixture. Mix just until no dry flour remains. Don’t overmix, to prevent adding too much air to the batter.
Cover with plastic wrap and chill in the fridge for at least an hour or overnight.
Using a cookie scoop (2 inches in diameter or 5cm), scoop the cookie dough and roll in the sugar. Place each cookie on a parchment-lined baking tray, at least 2 inches (5cm) apart.
Bake at 350F (180C) in a preheated oven on the middle rack for 10-11 minutes.
Remove them from the oven. Let them cool for 1-2 minutes, then carefully transfer the cookies to a cooling rack using a spatula. Enjoy!