Whisk the flour, baking soda, and salt together in a medium bowl. Set aside.

In a large bowl using a hand mixer or a stand mixer fitted with paddle attachment, beat the butter for 1 minute on high speed until creamy. Switch to medium-high speed and beat in the brown sugar and 1/4 cup (50g) granulated sugar until completely creamed and smooth, about 2 minutes. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Add the egg and beat until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed. Add the peanut butter and vanilla extract and beat until combined.

Add the flour mixture to the wet ingredients and beat on low speed until combined. The dough will be very creamy and soft. Cover and refrigerate the cookie dough for at least 1 hour, and up to 3 days.

Preheat oven to 350°F (177°C). Line 2 large baking sheets with parchment paper or silicone baking mats. (Always recommended for cookies.) Set aside. Also, make sure there’s room in your freezer because the baked cookies will need to be placed inside to prevent the chocolates from melting.

Scoop and roll cookie dough, about 1 heaping Tablespoon (around 25g) of dough each. If desired, roll each ball in 1/4 cup of granulated sugar. Arrange cookie dough balls on the baking sheet about 3 inches apart. Bake for 11–13 minutes or until the tops begin to slightly crack.

Remove cookies from the oven and allow to cool on the baking sheets for 5 minutes.

Gently press a chocolate heart candy into the center of each, then, using a thin spatula, immediately transfer the cookies to a large plate or a few smaller plates (gently—they’re soft). Place the plate(s) of cookies in the freezer for 10 minutes to quickly set the chocolate in the cookie.

Remove from the freezer and serve. Cookies stay fresh covered at room temperature for up to 1 week.