In a large mixing bowl, combine the softened salted butter and light brown sugar. Cream them together until light and fluffy, about 2-3 minutes.
Mix in the vanilla extract and 3/4 cup of creamy peanut butter until fully incorporated.
In a separate bowl, whisk together the all-purpose flour and kosher salt. Gradually add this dry mixture to the peanut butter mixture, mixing until just combined. Add water if necessary.
Divide the dough in half and shape each half into a log about 2 inches in diameter. Wrap each log tightly in plastic wrap and refrigerate for at least 1 hour.
Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Remove the dough from the refrigerator and slice the logs into 1/4-inch thick cookies. Place them on the prepared baking sheet.
Bake the cookies for 10-12 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.
Melt the chocolate using a double boiler or microwave until smooth.
Dip the bottom half of each cookie into the melted chocolate and allow excess to drip off. Sprinkle flaky salt on top before it sets.
Let the chocolate set at room temperature or refrigerate for about 15 minutes.
