Mix the milk, water, salt, and sugar.
Melt the butter in a medium pan, then pour the liquid ingredients in a slow and steady steam.
Heat it, then add the slowly flour.
Mix it well(with a hand mixer) to make sure it's lump free.
Cook it with constant stirring, it'll thicken and form a pastry.
Remove from the heat.
Add the eggs. One at a time, mix it well, then add the next and so on. (Use a hand mixer to make it easier for you)
Put it back to the heat, cook it with constant mixing for about 3-4 minutes.
Remove from heat and let it cool for a bit, preheat the oven in the meanwhile.
Prepare the instant vanilla pudding according to the instructions with the milk and the sugar.
Fill the vanilla pudding into a piping bag.
Fill the blackberry jam in another piping bag.
Use a nonstick pan or a baking/silicone sheet for the baking.
Fill the choux pastry in a piping bag. Use a big round/simple nozzle.
Pipe lines to the sheet. The size is your choice, but leave enough space between them to prevent them sticking together.
Bake it for 15-20 minutes or until they're a golden color. (Do not open the oven in the first 10-15 minutes or else they'll collapse!)
Let them cool a little after you get them out of the oven.
When they cooled down, fill them with the blackberry jam and the vanilla pudding. You can do this by cutting the eclairs in half and layer the fillings in them.
Melt the chocolate and dip the eclairs in it.
Let it cool and decorate them. * Optional