SECOND LAYER: Meanwhile in large bowl, combine confectioner's sugar (icing sugar), 1 Tbsp coffee crystals dissolved in 2 Tbsp hot water, softened butter and 1 egg (lightly beaten with a fork at room temperature.) Mix until thoroughly combined. (can use food processor or electric mixer). Put milk in pot over medium heat and scald (heat until bubbles appear around sides but milk is not a rolling boil). Add mixture from bowl and heat 7 minutes over medium heat , stirring frequently at first, constantly after the mixture bubbles. (If mixture starts to stick on bottom, lower heat slightly). Let cool slightly, then pour over first layer. Tilt pan to cover base layer evenly. Chill in refrigerator half an hour or more till set. THIRD LAYER: Combine 4 oz white chocolate with 1 Tbsp butter in double boiler and melt (or melt 1 -1 1/2 minutes in microwave on High and stir ). Spread over chilled second layer with spatula or blunt knife (layer will be quite thin). OPTIONAL MARBLED EFFECT: Melt 2 oz semisweet chocolate in double boiler (or in microwave 1 1 1/2 minutes on High and stir). Pour melted semisweet chocolate into small ziploc bag and seal. Snip corner of bag with scissors. Squeeze out horizontal lines of semisweet chocolate onto white chocolate layer. With a blunt knife, swirl the two chocolates together to create a marbled effect. Chill. Before the third layer is completely set, score into bars. VARIATION: Mocha Squares: substitute semisweet chocolate for white chocolate (this variation is easier as the middle layer and semisweet chocolate are similar in colour.) MAKES: approx 32 bars (they are very sweet, therefore the bars should be small)