Champagne Crepe Cake layered with Smoked Salmon, Avocado and Sour Cream

Crepes are really easy, if you get some elements right. Cook's Illustrated tested crepes and came to the following conclusions.

What doesn't matter

How long and vigorously you mix the batter
The type of flour you use - high or low protein
Resting or not
The liquid you use
This is because the gluten component of crepes is quite dilute. Crepes set because of the eggs, unlike pancakes which use gluten to turn the batter into a pancake. 

What does matter

Using a non stick pan
Using the correct heat
Heating the pan thoroughly

Crepe Batter

Whisk together
3 large eggs
375mls or 1½ cups sparkling wine
185g or 1½ cups plain flour
½ teaspoon salt
3 tablespoons butter
Filling 1
300g sour cream
Salt and pepper to taste
300g smoked salmon
Filling 2
4 avocados
Salt and lemon juice to taste
Directions Heat a non-stick frypan over medium-high heat for 10 mins to allow the pan to thoroughly and evenly heat.
Combine all ingredients in a blender and mix.
Brush the pan with a little melted butter.
Check temperature of pan by dropping a small amount of batter into the centre. It should brown in 20 seconds. If the pan is too hot or cool, adjust the temperature and give it a few minutes to adjust before testing again. (Take a note of the settings on your particular stove and you should only have to do this adjusting once.)
Pour batter into pan and tilt to form a crepe. I find 60mls is good for a 30cm pan.
Cook until top is dry, and the edges are crispy. Flip and cook until the other side is just starting to colour.
Remove crepe and layer on a plate. No need to layer plastic in between the crepes because they separate surprisingly easily. These can be made ahead. 
Repeat until all the batter is used. (A Chinese proverb says “First pancake never works”. True in life, and sometimes true with crepes. This recipe should make 8, but may make less due to 'accidents'. Drizzle said 'accidents' with lemon juice and sprinkle with a little sugar for a cook's treat!)
Filling 1 - Mix the sour cream with salt and pepper, stirring to break it up.
Filling 2 - Mash all ingredients together with a fork.
Assemble the cake Layer the fillings with the crepes, creating a striped effect. You can put the smoked salmon in a layer on it's own, or add it to a sour cream layer. As you layer the avocado and sour cream, pile a little more filling on the outsides than the insides to prevent it becoming dome shaped at the top.
Leave a few hours in the fridge to settle together.
Decorate the top as you like using extra sour cream to create a nice white background. To this add prawns, smoked salmon, cucumber, caviar, lemon twists, baby tomatoes halved, parsley or dill. Google "Smorgastarta" in Images to get ideas. 
Cut like a cake into 6-8 wedges.