Measure sides of trifle bowl or glass bowl with straight sides. Cut 1/3-inch-thick slices of pound cake so that cake will ring sides of bowl and cover bottom. You will also need a few additional slices for layering when you assemble the dessert.
Make a double boiler by filling stockpot halfway with water and fitting stainless-steel mixing bowl on top. Bring water to boil.
Remove mixing bowl from pot. Combine cornstarch, instant espresso, cup of the sugar and salt in bowl. Add cup milk and whisk to form paste. Put bowl back over boiling water.
In saucepan, bring remaining 1 cups milk and two-thirds of the chocolate to a boil. Watch carefully so milk doesn?t boil over. When milk is scalded, add the chocolate milk mixture to sugar mixture and let it cook on top of double boiler until it forms a thick pudding, stirring often but not continuously. Remove from heat, and allow to cool 10 minutes, still stirring every once in awhile so it will not form a skin.
Add chocolate liqueur to cooled coffee. Dip one side of each slice of pound cake in the coffee/chocolate liqueur mixture, and line sides and bottom of bowl, placing dipped side of the cake facing inward.
Using electric beater or whisk, whip the cream to soft peaks, adding remaining cup sugar and vanilla when cream starts to thicken. Chop remaining third of the chocolate.
To build your trifle, spoon a layer of pudding over the layer of cake in bottom of trifle dish, which should take one-third to one-half of the pudding. If your bowl has sloped sides, save more than half your pudding, since the next layer requires more pudding.
Spoon on a layer of whipped cream, and sprinkle with some of the chopped chocolate. Make another layer of dipped cake slices, then repeat sequence of pudding, whipped cream and chopped chocolate. You should now be at the top of bowl. Let chill at least 4 hours but no more than 24.