3 cups old-fashioned rolled oats
1 cup all-purpose flour
1 teaspoon fine salt
1/4 teaspoon baking soda
3/4 cup (1 and 1/2 sticks) unsalted butter, room temperature
1 cup packed light-brown sugar
1/2 cup granulated sugar
1/4 cup pure maple syrup
1 large egg
1 teaspoon pure vanilla extract
1 cup raisins (optional)
Preheat oven to 350 degrees. In a medium bowl, stir together oats, flour, salt, and baking soda. In a large bowl, using an electric mixer, beat butter and sugars on high until pale and fluffy, 3 minutes. Beat in maple syrup, egg, vanilla, and 1/4 cup water, scraping down bowl as needed. With mixer on low, beat in oat mixture in 2 additions until just combined.
You can fold in raisins, or I baked one batch plain and then added the raisins to the remaining batter.
Drop dough in rounded teaspoons, 2 inches apart, onto a parchment-lined baking sheet. Bake until edges are golden, about 10 minutes. Let cookies cool on sheet until set, about 2 minutes, then transfer to wire racks and let cool completely.