I found this recipe on Nestle's website about 3 years ago. I have made it numerous time. It requires a bit of work but the results are well worth it. The time for preparing and cooking is a guess, I have never timed it.
First of all cook the condensed milk. I prefer to do it in a pressure cooker; I find it safer. Here is what I do. Fill the pressure cooker with water to cover the condensed milk can inside. Place the cooker on the stove top and when it starts to boil count the time; 30 minutes is enough.
Let it cool completely.
It is very dangerous to open the can when it is hot. The hot sweet mixture inside will come out like a jet and it burns very badly.
For the biscuit:
Cream butter with sugar, egg and yolks in an electric mixer using the whisk attachment.
In another bowl mix flour, honey, bicarbonate of soda, baking powder and vanilla. Mix this into the butter mixture.
Work the dough until smooth.
Let it rest for 30 minutes.
On a floured board and using a rolling pin, roll the dough to a half (1/2) cm thickness.
With a round (5cm) biscuit cutter, cut biscuits and place on a prepared baking sheet.
Bake for 10 minutes in a medium oven (180°C).
They should be light brown when done.
Let it cool on a wire rack.
When the biscuits are cold, spread some of the "dolce de leche" (about 1 tsp for every two biscuits) and cover with another, making a sandwich.
Melt the chocolate by placing it in a bowl over hot water, not boiling water.
After the chocolate has melted bring it to the right temperature (you should feel it kind of icy when placed on your lips) for coating.
Drop each biscuit in the melted chocolate, lift with a fork, taking care to take off all the excess.
Place the covered biscuit on parchment paper and let it dry.