Sift flour with baking powder and salt. Cut 1 cup butter in small pieces. Add butter, ground almonds, sugar, lemon juice and rind to flour, Knead with hands until dough is very smooth and firm. Chill for at least 2 hours.
Roll small parts of dough between waxed paper to 1/8″ to 1/4″ thickness; keep remaining dough chilled until using. Cut into 1″ or 2″ rounds. Bake cookies on greased and floured cookie sheets in moderate oven (350 F) 10 minutes, or until golden. Remove cookies carefully. Very thin cookies are fragile.
After cooling, put two cookies together with jam, sandwich fashion. Melt chocolate and 1 tablespoon butter over hot, not boiling, water. Beat until smooth. If necessary, add up to 1 tablespoon hot water to achieve spreading consistency.
Frost Tortelettes on top and sides. Place half an almond on center of each cookie while frosting is still soft.
Makes about 5 dozen 1″ tortelettes, or about 2-1/2 dozen 2″ tortelettes