Prepare the chocolate cups: I cut squares of sponge that measured about 1 1/2-inches square. Wrap each square with plastic wrap. Dip each square into the tempered chocolate. Make sure the chocolate covers at least 1/2-inch up the side of the sponge mold. Set the chocolate square on a parchment paper lined baking sheet. Repeat to make as many chocolate cups as you would like. Wait until the chocolate sets. If necessary, place the chocolate squares in the refrigerator for about 5 minutes.
When the chocolate has set, gently squeeze the sponge and lift up to remove it from the chocolate. Do not press or pull too hard or you will break the chocolate.
Prepare the filling: Place a 1-quart saucepan half filled with water over high heat and bring to a simmer. Make a double boiler by setting a medium-size mixing bowl over the simmering water. Place the chopped chocolate in the mixing bowl and heat until completely melted. Stir occasionally and keep an eye on the chocolate as it melts so that it doesn’t burn. Once melted, remove the mixing bowl from the heat. Stir the chocolate until smooth and set aside until cool to the touch but not so cold that it begins to harden and set.
Place the peanut butter in a medium-size mixing bowl. Add the cooled chocolate and whisk together. This mixture will be stiff and begin to set quickly, so whisk vigorously and thoroughly to combine.
Place the chocolate peanut butter in a pastry bag with a medium-sized opening (no tip). Fill each chocolate cup to about 1/8 inch from the top. Let the peanut butter cups set at room temperature for about 1 hour, then serve. If you are in a hurry, you can place the peanut butter cups in the refrigerator for about 15 minutes. They can also be frozen for 2 weeks if well wrapped in plastic wrap. Thaw at room temperature before serving.
Jacques’ tip: To make a lighter dessert, add about 1 cup of crispy rice cereal (recommended: Rice Krispies). Sometimes I garnish this tiny treat with a dollop of whipped cream and fresh peanuts.