Stir together first three ingredients until sugar is dissolved; set aside 2 tablespoons mixture. Brush cut sides of ladyfingers evenly with remaining coffee mixture.

Stir together mascarpone cheese (can substitute cream cheese if desired), 1/2 cup powdered sugar, and chocolate syrup until blended. Spoon or pipe cheese mixture evenly onto 24 cut sides of ladyfinger halves; top with remaining ladyfinger halves, cut sides down.

Melt chocolate morsels, butter, and cream in double boiler.* Place chocolate mixture in a small heavy-duty zip-top bag; seal bag. Snip a tiny hole in one corner of bag and drizzle over éclairs. Let stand until firm.

Stir together reserved coffee mixture and remaining 1 cup powdered sugar, stirring until blended. Place coffee-powdered sugar mixture in a small heavy-duty zip-top bag; seal bag. Snip a tiny hole in one corner of the bag. Drizzle éclairs evenly with coffee-powdered sugar mixture. Place on a serving platter, cake stand, or in candy boxes, if desired.