Line a baking sheet or large flat tray with parchment paper or wax paper. Make sure there is enough room in your refrigerator for the tray to sit flat.
Place the peanut butter in a small bowl. If you prefer a sweeter filling, stir in the powdered sugar until smooth. The sugar is optional, as the chocolate coating already adds sweetness.
Spread approximately 1 teaspoon of peanut butter onto the flat side of one Ritz cracker. Place another cracker on top and gently press them together. Repeat with the remaining crackers and filling.
Arrange the cracker sandwiches on the prepared tray and refrigerate for 10–15 minutes. Chilling helps firm the filling and makes the sandwiches easier to dip.
Place the chocolate chips in a microwave-safe bowl. Heat in 20–30-second intervals, stirring after each interval until the chocolate is smooth. Add the coconut oil if desired to make the coating thinner and easier to dip.Alternatively, melt the chocolate in a heatproof bowl over a saucepan of gently simmering water. Keep water away from the chocolate to prevent it from becoming grainy. Using a fork, dip each chilled sandwich into the melted chocolate. Turn it gently to coat all sides, then lift it out and allow excess chocolate to drip back into the bowl.
Place each coated sandwich on the lined tray. While the chocolate is still wet, add sprinkles, crushed peanuts, or a tiny pinch of flaky sea salt. You can also drizzle white chocolate over the top after the main coating begins to set.
Refrigerate the cookies for 20–30 minutes, or until the chocolate coating is completely firm. Once set, transfer them to an airtight container and serve chilled or at cool room temperature.