• Thaw store-bought puff pastry sheets according to package instructions. I use pepperidge farm puff pastry sheets to make these tarts.
  1 box Puff pastry

Make apple tart filling

• Peel and chop apples into small cubes.
  3 Apples
• In a non-stick pan on medium-high heat, melt butter. Add chopped apples, brown sugar, and salt to this, and saute for about 8 mins.
  2 tablespoon Butter, ½ cup Brown sugar, Salt, a pinch
• Then, add cinnamon powder and roasted nuts (optional) and saute for another 2 minutes. Remove from heat and allow the apple filling to cool to room temperature.
  1 teaspoon Cinnamon, ¼ cup Roasted nuts
• You can store the apple filling in the refrigerator for up to 7 days. 

Individual apple tarts squares

• Preheat the oven to 400 F.
• Dust the flour on your working surface and place one thawed puff pastry sheet.
  All-purpose-flour, for dusting
• Lightly roll the sheets till they are about ½ inch longer on each side, using a rolling pin.
• Then, divide them into four pastry squares using a pizza cutter or a kitchen knife.
• Place these pastry squares on a baking tray lined with parchment paper.
• Brush all edges of each square portion with egg wash - this gives the baked apple tart its golden brown color. You can also sprinkle some sugar. 
  1 Egg
• Fill the centers of each square with about two spoonfuls of prepared apple filling. 
• Repeat the above steps for the remaining puff pastry sheet.
• Bake the tart for 20 minutes or until the edges turn golden brown and crispy.
• Let the tarts cool down for a few minutes before serving.
• You can serve apple tarts as a breakfast with a cup of coffee, a quick snack, or as an after-meal dessert with a scoop of ice cream or whipped cream.