Spray the inside of your slow cooker with cooking spray. Line the bowl in an “x” using two 4” to 5” strips of parchment paper. Beat the butter and sugars with an electric mixer until light and fluffy, about 2 minutes. Then add in egg and vanilla extract and mix thoroughly.

Add flour, baking soda, and salt and mix until combined perfectly. Mix in the chocolate chips. Pour cookie dough into the slow cooker and smooth down the top with a spatula.

Cover with the lid and cook on low for 5 to 6 hours (or high for 2 1/2 to 3 hours), until the center of the cookie is slightly soft. You can leave the cookie in the slow-cooker to keep warm for up to 3 hours. Remove the cookie container from the slow cooker and place it on a cooling rack. Let sit till cool enough to eat. Use the parchment paper to remove the cookie then slice, and serve and enjoy.