COOKIES: In a mixer with paddle attachment cream the butter and the sugar.
Add the egg whites gradually and then mix in the vanilla and lemon extracts.
Add the flour and mix until just well mixed. Don’t over mix.
Fit the decorating tip onto a corner of the plastic bag, snip the corner, and attach the coupler. Fill the bag with the cookie batter. Pipe 1-inch (2.5 cm) sections (I made mine longer, about 2 inches/5 cm) of batter onto a parchment-lined sheet pan, spacing them 2 inches/5 cm apart as they spread.
Bake in preheated oven for 10 minutes or until light golden brown around the edges. Let cool on the pan. Continue with the remaining cookie batter.
CHOCOLATE FILLING: While waiting for the cookies to cool, in the small saucepan over medium flame, scald the cream.
Put the chopped chocolate into the medium mixing bowl and pour the hot cream over the chocolate. Whisk to melt chocolate, then add the orange zest and blend well.
Set aside to cool. The mixture will thicken as it cools.
10. ASSEMBLE: Spread a thin amount of the filling onto the flat side of a cookie while the filling is still soft and press the flat side of a second cookie on top. Continue with remaining cookies and filling.