Cream the Butter, Peanut Butter, and Sugars: In a large mixing bowl, combine ½ cup softened unsalted butter, ¾ cup creamy peanut butter, ¾ cup packed light brown sugar, and ¼ cup granulated sugar. Beat with an electric mixer on medium speed for approximately 2–3 minutes, until the mixture looks creamy, slightly lighter in color, and evenly combined. Scrape down the sides of the bowl as needed. The mixture should be thick and smooth, without visible streaks of butter.

Add the Egg and Vanilla: Add 1 large egg and 1 teaspoon pure vanilla extract to the peanut butter mixture. Beat on low to medium speed until the egg is fully incorporated. The mixture should become smooth and cohesive. Scrape the bowl again to make sure no unmixed ingredients remain near the bottom. Avoid excessive mixing once the egg has been incorporated.

Combine the Dry Ingredients: In a separate medium bowl, whisk together 1½ cups all-purpose flour, ½ teaspoon baking soda, and ½ teaspoon fine sea salt. Whisk until the baking soda and salt are evenly distributed throughout the flour. This helps the cookies rise and brown consistently.

Make the Cookie Dough: Add the dry ingredients to the peanut butter mixture in two additions. Mix on low speed just until the flour disappears and a soft dough forms. The dough should be thick, slightly tacky, and easy to scoop. If the dough looks crumbly, gently press a small amount together with your fingers. It should hold its shape without falling apart.

Chill the Dough: Cover the mixing bowl and refrigerate the cookie dough for 30 minutes. Chilling firms the butter and helps prevent excessive spreading during baking. The chilled dough should feel slightly firmer but remain easy to scoop. If it becomes too firm after longer refrigeration, let it stand briefly at room temperature before portioning.

Preheat the Oven and Prepare the Baking Sheets: Near the end of the chilling time, preheat the oven to 350°F (175°C). Position a rack in the center of the oven. Line two large baking sheets with parchment paper. Using a 1½-tablespoon cookie scoop, portion the dough into 24 evenly sized balls. Roll each portion gently between your palms to form a smooth ball.

Arrange and Flatten the Cookies: Place the cookie dough balls on the prepared baking sheets, leaving approximately 2 inches (5 cm) between each one. Gently press each dough ball with your palm or the bottom of a glass until it is approximately ½ inch (1.3 cm) thick. Do not flatten the cookies too thinly. Keeping them slightly thick helps maintain soft, chewy centers. For a traditional peanut butter cookie appearance, you can lightly press a crisscross pattern into the tops with a fork.

Bake Until the Edges Are Set: Bake one sheet at a time for approximately 10–12 minutes, until the edges look set and lightly golden. The centers should still look slightly soft but should no longer appear wet or glossy. Avoid waiting for the entire surface to become deeply browned, as the cookies will continue setting as they cool. If the cookies spread unevenly, gently nudge their edges into a round shape with a spoon immediately after removing them from the oven.

Cool the Cookies Completely: Allow the cookies to rest on the baking sheet for approximately 5 minutes. They will be delicate immediately after baking but should become firmer as they cool. Transfer them carefully to a wire rack and allow them to cool completely for approximately 15 additional minutes. Make sure the cookies are no longer warm before dipping. Warm cookies can cause the chocolate to become messy and prevent an even coating.

Melt the Chocolate: Place 8 ounces finely chopped semisweet chocolate in a clean, dry microwave-safe bowl. Microwave at 50% power in 20-second intervals, stirring thoroughly between intervals, until the chocolate is nearly melted. Continue stirring until the remaining pieces dissolve and the chocolate becomes smooth and glossy. If the chocolate is too thick for dipping, stir in the optional 1 teaspoon refined coconut oil until fully incorporated. Alternatively, melt the chocolate in a heatproof bowl set over a saucepan of gently simmering water, making sure the bowl does not touch the water. Avoid overheating or allowing water to enter the chocolate, which can cause it to seize.

Dip the Peanut Butter Cookies: Hold one completely cooled cookie by its edge and dip approximately half of it into the melted chocolate. Lift the cookie slowly and allow excess chocolate to drip back into the bowl. Gently scrape the bottom edge against the side of the bowl if needed. Place the dipped cookie on a parchment-lined baking sheet. Repeat with the remaining cookies, reheating the chocolate gently if it begins to thicken.

Add the Optional Garnishes: While the chocolate is still wet, sprinkle the chocolate-covered portion of each cookie with the optional finely chopped roasted peanuts or a small pinch of flaky sea salt. The peanuts provide additional crunch, while the flaky salt adds a savory contrast to the chocolate. Apply the garnishes before the chocolate begins to set so they adhere properly.

Let the Chocolate Set: Leave the dipped cookies undisturbed at cool room temperature for approximately 30 minutes, or until the chocolate coating is firm enough to handle. The setting time will depend on the type of chocolate and the temperature of the room. Chocolate melting wafers generally set more firmly than untempered regular chocolate. If needed, refrigerate the cookies briefly to help the coating firm up, but avoid prolonged chilling that may encourage condensation when the cookies return to room temperature. Once the coating has set, the cookies are ready to serve or store.