Step 1

the milk (and cream if using) over medium heat in a large saucepan with high sides and double or triple bottom.

Step 2

the sugar when it’s warm and mix.

Step 3

the baking soda and stir until it dissolves.

Step 4

When it starts to boil, lower the heat to a minimum but keep it simmering.

Step 5

At this point is where you can add a plate upside down, glass marbles, or some other small glass object that can withstand the heat. What they do is move around so it ‘stirs’ the mixture and also helps with crystallization.

Step 6

it reduce, stirring every so often, about an hour, or an hour and a half. This depends on the amount of milk you’re using and the amount of heat.

Step 7

It darkens from the bicarbonate and thickens. If you added a plate you can stir once in a while, but it not, you should stir more often.

Step 8

At some point, usually an hour from the moment it starts to simmer, it gets quite dark and thickens. At this point, it’s almost ready. Maybe a few minutes more. Make sure you take out the plate and stir constantly during these last moments.

Step 9

If you put a little on a plate it will run immediately, be quite liquid. It will thicken a lot as it cools and even more in the refrigerator.

Step 10

from the heat, add vanilla and salt if using, transfer to a bowl and let cool. If you stir over a bowl with ice water it will cool faster and generally makes it creamier because there’s a smaller chance of crystallization.

Step 11

at the end before refrigerating to make it as creamy as possible.

Step 12

a jar and keep refrigerated.

Step 13

cornstarch and milk in a small bowl or cup.

Step 14

the dulce de leche in a small saucepan over low heat.

Step 15

constantly, and when the dulce de leche becomes more liquid, add the cornstarch slowly while stirring with a wooden spoon.

Step 16

the mixture to a slow boil, stirring all the time. You don't want the mixture to stick.

Step 17

for about 2 minutes, being careful it doesn't burn in the bottom of the pan. Check that it has somewhat thickened, but remember it will completely set after it's cooled and refrigerated.

Step 18

cool completely and refrigerate for 1 hour before using, or for several weeks in a closed jar.

Step 19

50g (3 1/2 tablespoons) butter in a medium saucepan.

Step 20

a can of condensed milk (400g / 14oz) and 200g (7oz) regular dulce de leche.

Step 21

over low heat until it thickens and let cool before using.