Preheat oven to 250°F. Using the straight side of the 2 in. round cutter from the Double Cut-Outs Set, trace 36 circles onto parchment paper. Flip parchment over and place on cookie pan.
In large bowl, whip Meringue Powder, water and salt with electric mixer on high speed until soft peaks form. With mixer running, gradually add sugar and 1 teaspoon vanilla extract. Whip until stiff peaks form and mixture triples in volume.
Using a decorating bag fitted with tip 1A and using the traced circles as a guideline, pipe 2 in. flat discs of meringue about 1/4 to 3/8 inch tall. Flatten points with tip of finger.
Bake 35-40 minutes or until outsides of meringues feel firm and crisp. Cool completely on pan.
In large bowl, whip cream and confectioners? sugar on high speed until very soft peaks form. Add Piping Gel and remaining 1 teaspoon vanilla extract, and whip until stiff peaks form, scraping down bottom and sides of bowl as necessary.
Using a decorating bag fitted with tip 1M, cover 12 of cooled meringues with a rosette of whipped cream. Top with a second meringue and repeat with whipped cream. Invert remaining meringues and press into whipped cream so flat sides are facing up. Freeze for at least 30 minutes. Refrigerate remaining whipped cream until ready to ice.
Remove half of the merveilleux from freezer for icing; keep other half in freezer while working. Spread a very thin layer of whipped cream over the sides of the merveilleux. Roll in sprinkles to cover. Using a decorating bag fitted with tip 1M, cover top with a rosette of whipped cream.
Refrigerate at least 3 hours before serving so meringues soften. Merveilleux are best eaten within 24 hours so the meringue cookies maintain some of their crisp, chewy texture.