Step 1: Preheat the Oven and Prepare the Baking Sheet

Start by preheating your oven to 350°F (175°C). This ensures that the cookies bake evenly and the dough doesn’t spread too much. Line a baking sheet with parchment paper or a silicone baking mat to prevent the cookies from sticking and to help with even baking.

Step 2: Mix the Dry Ingredients

In a separate bowl, combine 3 cups all-purpose flour, 2 teaspoons baking soda, 1 teaspoon cornstarch, and 1 teaspoon salt. Whisk the ingredients together until they’re well combined. Set this bowl aside to use later.

Step 3: Cream the Butter and Sugars

In a large mixing bowl, combine 1 cup unsalted butter, 1 cup brown sugar, and ½ cup granulated sugar. Using a hand mixer or a stand mixer, beat the mixture on medium speed for 2-3 minutes until the mixture is light and fluffy. This step is important because the air incorporated into the butter and sugar creates a softer texture for the cookies.

Step 4: Add the Eggs and Vanilla

Next, add the 2 large eggs, one at a time, and mix well after each addition. Then, add 1 tablespoon vanilla extract and continue mixing until the dough is smooth.

Step 5: Combine the Dry and Wet Ingredients

Gradually add the dry ingredients to the wet ingredients, mixing on low speed to avoid flour spilling everywhere. Once the dough comes together, stop mixing. Overmixing can cause the cookies to be dense instead of chewy.

Step 6: Add the Chocolate Chips and Chunks

Add 8 ounces of semi-sweet chocolate chips and 4 to 8 ounces of chocolate chunks (optional). Use a spatula to gently fold them into the dough. Be careful not to overmix, as this can make the cookies tough.

Step 7: Portion the Dough

Using a spoon or cookie scoop, portion out ¼ to ½ cup of dough for each cookie. Place the dough portions 3 inches apart on the prepared baking sheet. If you want thicker cookies, go for the larger portions of dough. The cookies will spread a little as they bake, so make sure to leave enough space between each one.

Step 8: Bake the Cookies

Bake the cookies in the preheated oven. For ¼ cup portions, bake for 12-15 minutes. For ½ cup portions, bake for 15-20 minutes. Keep an eye on the cookies—once they’re golden brown around the edges and slightly underbaked in the center, they’re ready to come out. The underbaked center will firm up as the cookies cool, ensuring they stay chewy.

Step 9: Cool the Cookies

Let the cookies cool on the baking sheet for 15 minutes before transferring them to a wire rack to cool completely. This cooling time allows the cookies to firm up without losing their chewy texture.