In a mixing bowl, add in the butter and brown sugar. Mix on medium until light and fluffy. Scrape down the sides.
Add in the egg and vanilla and mix on medium until combined. Scrape down the sides of the bowl.
Add in the pudding, flour, and baking soda. Mix on low until just combined.
Stir in the chocolate chunks with a spatula.
Using a cookie scoop, scoop out cookie dough onto a baking sheet. Space about 2 inches apart on the cookie sheet.
Place in the oven for about 8-9 minutes or until the edges are golden brown. My cookie scoop is quite small so it took a shorter amount of time than it would if you make huge cookies.
Let cool for 5 - 10 minutes on the baking sheet and then place onto a cooling rack.