Place the heavy cream in a small saucepan and bring to a simmer.
Place the semisweet chocolate in a small heatproof bowl. Place the white chocolate in a separate small heatproof bowl. When the cream has come to a simmer, pour 3/4 cup of the hot cream over the semisweet chocolate and let sit for 1 minute, undisturbed. Pour the remaining hot cream over the white chocolate and allow to sit for 1 minute. Whisk the semisweet chocolate-cream mixture until smooth. Repeat with the white chocolate mixture. Cover both bowls loosely with plastic wrap and transfer to the refrigerator. Chill, stirring occasionally, until both mixtures have cooled and thickened but are still pourable. One at a time, beat each mixture with an electric mixer until soft peaks form. Do not overbeat - the mixture should appear smooth, glossy, and just barely stiff, not clumpy or dry.
Lightly grease a 3 by 5-inch individual loaf pan or small rectangular terrine and line with plastic wrap.
Carefully spoon half of the semisweet chocolate mixture into the bottom of the pan, smoothing the mixture into the corners. Trim two of the pound cake slices so that together they form 1 layer that precisely fits the size of the pan and press lightly onto the top of the chocolate mixture. Brush the cake with some of the Amaretto. Spoon all of the white chocolate mixture carefully into the pan and use a spoon or spatula to smooth the top and force mixture into the corners. Top with a layer of pound cake as before and brush with some of the Amaretto. Spoon the remaining semisweet chocolate onto the top and smooth as before. Top with another layer of pound cake and brush with Amaretto. Bring the extra plastic wrap up over the sides of the pan and cover the top of the pave. Press lightly to compact slightly. Transfer to the refrigerator until thoroughly chilled, at least 3 hours or up to overnight.
When ready to serve the pave, gently remove from the pan by grasping the plastic wrap and pulling upward. Transfer to a small serving plate and set upright so that the narrower edge is now on top. Using a warm knife, slice the pave into 1/2-inch slices and divide between serving plates. Spoon the Amaretto CrËme Anglaise over and around the pave and garnish with chocolate curls or a sprig of fresh mint, as desired.
Yield: 2 to 4 servings