Preheat your oven to 375ºF (190ºC) and prepare four large baking sheets lined with silicone mats or parchment paper.

Melt 1/2 cup of unsalted butter with 1 cup of light brown sugar over medium heat, stirring continuously until smooth (3-5 minutes).

Remove from heat and stir in 1 cup of old fashioned oats, 1 Tbsp + 1 tsp of all-purpose flour, and 1/2 tsp of fine salt until thoroughly combined.

Whisk in 1 large egg and 1 tsp of vanilla extract until completely integrated.

Drop small mounds of batter onto baking sheets, leaving at least 2 inches between each cookie.

Bake for 5-7 minutes until edges are golden brown and centers are slightly puffed.

Allow cookies to cool on trays for about 15 minutes before transferring to wire racks.

Continue to scoop and bake remaining batter until all cookies are completed.