Warm the oven up to 350°F. Put a silicone baking mat or parchment paper on a big baking sheet and set it aside.
Step 2
With a hand-held mixer, beat the butter, brown sugar, and powdered sugar in a medium-sized bowl until the mixture is light and fluffy.
Step 3
Add the egg yolk and vanilla and mix well, stopping to scrape the sides of the bowl as needed.
Step 4
Mix the flour, baking soda, and salt in until they are all fully mixed in. Then add the semisweet chocolate chips and rolled oats and mix them in until they are fully mixed into the dough.
Step 5
Place two-teaspoon-sized chunks of dough on the baking sheet that has been prepared. You should get eight to nine cookies this way.
Step 6
For 9 to 11 minutes, bake at 350°F. Take the cookies out of the oven and let them cool for 5 minutes on the baking sheet.
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