Step 1

Preheat the oven to 350.

Step 2

In a medium bowl, cream together the butter, brown sugar and vanilla for 1 minute.

Step 3

Add the egg yolk, and mix until combined.

Step 4

Combine the oats with the flour, corn starch, baking powder, baking soda, and salt.

Step 5

Mix well.

Step 6

Add the dry ingredients in two batches to the wet ingredients, and beat to combine.

Step 7

Scoop marble sized dough balls (about a tsp. each cookie) out onto a cookie sheet.

Step 8

You will get about 30 cookies.

Step 9

Bake for 6-7 minutes, and don't be afraid for the cookies to get a little color on them.

Step 10

Remove from oven and leave cookies on baking sheet for another minute. Then transfer to parchment paper or wire rack.