In a large saucepan, melt butter over low heat.

Add the marshmallows to the saucepan and stir continuously until they are completely melted and smooth.

Remove the saucepan from the heat and add the vanilla extract.

Pour the Rice Krispies cereal into the saucepan and stir until it is evenly coated with the marshmallow mixture.

Press the mixture into a greased 9x13-inch baking dish, using a greased spatula or wax paper to smooth it out.

Put in the refrigerator to set for 15 minutes.

Once the Rice Krispies are set, use a heart-shaped cookie cutter to cut out heart Rice Krispie treats.

Melt the white chocolate chips in small microwave-safe bowl in 30-second increments. Dip the Rice Krispie hearts into the melted chocolate.

If desired, sprinkle Valentine's Day-themed sprinkles or candy hearts on top for a festive touch.

Allow the treats to set for about 10 minutes.

Serve the Valentine's Day Rice Krispies treats on a platter or package them in festive bags to give as gifts.