Line 9 1/2"x13" baking pan {1/4 sheet pan size} with parchment paper and line with 24 Ritz crackers, if you like. These bars will work with or without the extra crackers on the bottom. If you choose to not line the bottom with crackers, lightly spray with nonstick cooking spray and set aside.
Coarsely crush the remaining two sleeves of Ritz crackers and set aside.
In a large pot or deep nonstick skillet, melt butter over medium heat. Stir in sugar and evaporated milk and bring to a bubble. Simmer gently for 5 minutes, then remove from heat and stir in marshmallow fluff, peanut butter and vanilla. Then dump in the crushed crackers and stir.
Pour into prepared pan. Grease fingers and press evenly into pan. Refrigerate for 10 minutes.
Melt chocolate in a small bowl using the microwave, stirring every 20-30 seconds to prevent burning. Drizzle chocolate over bars, then sprinkle with sea salt {as much or as little as you'd like}. I used about 2 teaspoons.
Refrigerate another 10 minutes or until chocolate is set, cut into bars and serve.