Stir together first 3 ingredients until sugar is dissolved; set aside 2 tablespoons mixture. Brush cut sides of ladyfingers evenly with remaining coffee mixture.
Stir together mascarpone cheese, 1/2 cup powdered sugar, and chocolate syrup until blended. Spoon or pipe mascarpone cheese mixture evenly onto 24 cut sides of ladyfinger halves; top with remaining ladyfinger halves, cut sides down.
Microwave chocolate morsels, butter, and cream at HIGH 30 seconds or until melted, stirring twice. Place chocolate mixture in a small heavy-duty zip-top bag; seal bag. Snip a tiny hole in 1 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 1 corner of bag. Drizzle eclairs evenly with coffee-powdered sugar mixture. Place on a serving platter, cake stand, or in candy boxes, if desired.
*1 (8-ounce) package cream cheese, softened, may be substituted.