Peanut Butter Chocolate Chip Cookies

9 Preheat the oven to 350°F / 177°C. Line a sheet pan with parchment paper or a silicon baking mat. 
0 In a small bowl, whisk together the flour, baking soda, cornstarch, and salt. Set aside.
1 Using a standing mixer or hand mixer, beat butter, both sugars, and peanut butter until light and fluffy, 2 to 3 minutes.
2 Add the eggs and vanilla and mix on low-medium until evenly combined. 
3 Add the dry ingredients to the bowl all at once and mix on low just until combined. 
4 Mix in the chocolate just until combined. (See note.)
5 The cookie dough will be very soft. In order to make it easier to handle, you can refrigerate it for up to 30 minutes, but you can also proceed immediately by using a 1 1/2 tablespoon cookie scoop or a spoon to drop balls of dough onto the prepared cookie sheet. Leave a few inches between the cookies - they will spread out as they bake. 
7 Bake just until the edges darken slightly. The centers should still look very pale and soft, 9 to 12 minutes.
8 As soon as you remove the pan from the oven tap it firmly on the counter a few times to deflate the cookies. (This will compress the centers, making them soft and chewy.) 
10 Let the cookies cool on the sheet pan for at least 5 minutes. (Note: When they come out of the oven, these cookies will be very tender and break easily. Leaving them on the hot sheet pan helps them to hold their shape while still staying very soft and tender.) Enjoy!
11 Store cookies in a sealed container at room temperature for up to 3 days.