Make Dulce de Leche
Carefully make 3 holes in the top of the can by hammering a nail through the lid.
Set the can inside of a pot and fill with water until the water is about 3/4 the way up the side of the can.
Bring to barely a simmer and let it go for 4 hours.
After 4 hours, carefully remove can from hot water and open. Pour contents into a bowl & whisk about 4 – 5 minutes until smooth.
Make Popcorn Crust
Combine popcorn, butter, sugar, salt & pepper in food processor and blitz until rubble.
Press the popcorn mixture into tart mold(s).
Use a small measuring cup or glass with a flat bottom to press into the sides and bottom of tart to make sure everything is even.
Refrigerate for an hour. This will allow everything to set up, the butter to harden, etc.
Place into a 375 degree oven for 10 minutes. Remove from oven and let cool completely.
Assemble tart
Pour dulce de leche into cooled popcorn crust and top with flakes of sea salt.