Chill two medium mixing bowl. Line a 5-cup round-bottomed bowl or mold with plastic wrap, letting the edges of the wrap hang over the sides of the bowl or mold.
In a shallow bowl combine the hot coffee, coffee liqueur (if desired), and the 1 teaspoon sugar; stir to dissolve sugar. Brush rounded sides of ladyfingers with the coffee mixture.
Line the bottom and sides of the bowl or mold with Ladyfingers, placing the rounded side outward. Fill any gaps with ladyfinger trimmings so that the lining is solid. Drizzle with any remaining coffee mixture. Reserve remaining ladyfingers. Cover and chill the lined bowl or mold until needed.
In a medium mixing bowl beat cream cheese, the 1/4 cup sugar, and vanilla with an electric mixer on medium speed until fluffy; set aside.
In 1 of the chilled bowls stir vanilla ice cream, pressing it against the side of the bowl with a spoon, just until softened (do not let ice cream get too soft).
Immediately fold the softened vanilla ice cream and chocolate pieces into the cream cheese mixture; cover and freeze for 3 to 4 hours or until stiff, stirring mixture occasionally so chips don't sink. Spread cream cheese mixture over the ladyfingers in the bowl or mold, spreading up the sides, to make a lining. Cover with heavy foil and freeze for 2 to 4 hours or until firm.
In the other chilled bowl soften coffee ice cream as directed for vanilla. Spoon on top of the cream cheese mixture, spreading smoothly. Cover surface of the bombe completely with the remaining ladyfingers. Fold excess plastic wrap over surface. Cover tightly with heavy foil. Freeze until firm or up to 1 month.
To serve, remove foil and invert bombe onto a serving platter; remove bowl or mold and plastic wrap. Let stand at room temperature for 20 to 30 minutes to soften slightly before cutting.
Meanwhile, if desired, in a small saucepan heat and stir the Coffee-Hot Fudge Sauce or fudge ice-cream topping. Cut the bombe into wedges and transfer to dessert plates. Drizzle each wedge with some of the sauce; pass any remaining sauce. Makes 8 to 10 servings.
Coffee-Hot Fudge Sauce
Place miniature semisweet chocolate pieces and butter in a small heavy saucepan over very low heat, stirring constantly until smooth. Add sugar and instant coffee crystals. Gradually stir in evaporated milk. Bring to boiling; reduce heat. Boil gently over low heat 8 minutes, stirring frequently. Remove from heat. Makes 1-1/2 cups.