In a large mixing bowl, cream together the butter, brown sugar, and vanilla until light and fluffy, about 3-5 minutes. Add the peanut butter, and mix until combined. Add the flour and salt, beat until combined and the dough forms a ball. If the dough seems too crumbly, add water, 1 tablespoon at a time, until it comes together. The dough should not be overly sticky. 2. Divide the dough in half. Place each ball on a large piece of plastic wrap. Using your hands, shape it into a rectangle about 6 inches long and about 2 inches wide. Wrap the dough up in the plastic wrap and place in the freezer for 30 minutes, or the fridge for 3 hours or overnight. If you have an empty tin foil box (yes, the one you get your tin foil out of) laying round, fit your dough roll inside to help the dough set in a rectangular shape (see above photo). Alternately, you can make circle cookies as well. 3. Preheat oven to 350 degrees F.Unwrap the dough and cut the rectangular log into 1/3 inch slices. Arrange the slices 1 inch apart on a baking sheet. Bake the cookies for 10-14 minutes, until the edges are golden brown. Let cool 10 minutes on the baking sheet and then transfer to a cooling rack.Spread each cookie with peanut butter and place on a parchment lined baking sheet. Transfer to the freezer and freeze 20 minutes. This makes coating in chocolate easier.Melt the chocolate and let cool 10-20 minutes prior to dipping. Holding the cooking on the ends of a fork, dip each cookie in melted, cooled chocolate and place on a parchment lined baking sheet. Repeat with the remaining cookies. Sprinkle with flaky sea salt. Place the cookies in the fridge to set for 20 minutes. Store in an air-tight container for up to 3 days.