1. Line an 8-inch or 9-inch square baking dish with parchment paper and set aside. (You can use a 9x13-inch if you want thinner bars.)
2. In a large mixing bowl, stir together the oatmeal, 1 cup of the chocolate chips, the peanut butter and vanilla extract; set aside.
3. In a small saucepan, combine the sugar, milk, butter and salt over medium heat. Bring to a full boil (there should be bubbles covering the entire surface) and boil for 2 minutes.
4. Immediately pour the hot mixture (carefully!) over the oatmeal mixture and quickly stir to combine, ensuring that all of the oatmeal mixture has been moistened. Turn the mixture into the parchment-lined pan and use the back of a spoon to press it evenly into the pan. Sprinkle the remaining 1 cup of chocolate chips over top and gently press them into the top of the mixture.
5. Allow the bars to sit at room temperature to set up, which takes about 30 minutes. Use the edges of the parchment paper to lift the bars out of the pan and cut into squares. Store in an airtight container at room temperature for up to 1 week.
Note: Like any no-bake cookie, the final texture of these really depends on how long you boil the sugar mixture. If it doesn’t boil long enough, the cookie mixture will be too soft; if you boil too long, they could turn out dry and crumbly. I like to set a timer just to be sure.