In a large mixing bowl, combine the melted and cooled salted butter, creamy peanut butter, granulated sugar, and vanilla extract. Mix until well combined.
Gradually add the powdered sugar to the peanut butter mixture, mixing until the filling is smooth and thick.
Press the peanut butter filling into a heart-shaped cookie cutter placed on parchment paper. Repeat until all filling is shaped. Freeze for about 30 minutes to firm up.
In a microwave-safe bowl, combine the semi-sweet chocolate chips and shortening. Heat in 30-second intervals, stirring until melted and smooth.
Dip each firm peanut butter heart into the melted chocolate, coating fully. Place coated hearts back on parchment paper to set.
Sprinkle colorful sprinkles on top before chocolate sets, if desired.
Melt white chocolate chips with the teaspoon of shortening in microwave. Drizzle over the chocolate-covered hearts for an elegant finish.
Allow hearts to set at room temperature or refrigerate until chocolate coating is fully set.