Doublecrust Apple Pie

• 3 firm tart apples
• 2 crust pie above filling
• 130 gr sugar
• 26 gr butter (unsalted)
• 16 ml lemon juice
• 4 gr sugar for finishing the top of the pie (optional)
• 3 gr cinnamon (ground)
• 1 gr egg well with a of salt (beaten)