THAW pastry sheets at room temperature for 30 minutes. Preheat oven to 375 degrees F. Mix 1 egg and water.
PLACE almonds and sugar in food processor. Cover and pulse on and off until finely ground, about 1 minute. Add 1 egg and continue to pulse until smooth paste forms. Add butter, a little at a time, pulsing after each addition. Scrape down sides of bowl. Add remaining egg and pulse until smooth. Add flour and rum and pulse until just blended.
UNFOLD 1 pastry sheet. Place sheet in 9" tart pan. Top with almond mixture. Unfold remaining pastry sheet and place on top. Trim pastry to fit. Crimp edges and cut slits in top. Brush with egg mixture.
BAKE 45 minutes or until golden brown. Cool in pan on wire rack. Serve with chocolate sauce, if desired.