Craquelin:

1. Add the butter, light brown sugar, granulated sugar and vanilla to a bowl. Whisk on medium speed for 1-2 minutes until combined and creamy. Scrape the bowl
2. Add the flour, and whisk on low speed until the mixture starts to look like a crumble. It should stick together when you apply pressure (just like pie dough)
3. Place a silicone mat or parchment paper sheet on the back of a 9x13" baking tray. Add the craquelin mixture in the middle and press it into a disc. Cover with another sheet of parchment paper, and use a rolling pin to roll it out into a thin sheet (~2mm thick, or similar to pie crust)
4. Transfer to the fridge or freezer while you make the choux pastry 

Choux pastry:

1. Pre-heat your oven to 390F (conventional, no fan) and prepare 2-3 large baking sheets. Place them upside down, and line with parchment paper. Use a pencil and the back of a large piping tip to make 1.5" circle markings on the parchment paper, leaving at least 1.5" between each circle. If you only have 1 baking sheet, don't worry, as you can bake in batches!
2. Add the water, milk, butter, vanilla, sugar and salt to a light colored saucepan. Put on the stove on medium heat, and stir and cook until the butter has melted and the mixture starts to boil
3. Remove from the heat, and add the flour. Use a wooden spatula to mix and fold the flour into the wet ingredients, breaking any lumps, until it comes together into a smooth ball
4. Place the pan back on the heat on low flame, and cook and stir (using a press and swirl motion) for 2 minutes. This will dry out the dough and it will start to leave a thin film on the bottom of the pan (this doesn't always happen if you're using a nonstick pan, so don't worry too much). Remove from the stove and let cool for 5 minutes
5. In a separate bowl, add the 4 large eggs, and whisk them lightly to break them down
6. Transfer the choux pastry dough to the bowl of your stand mixer with a paddle attachment (you can also use a hand mixer, or just a rubber spatula and your hands if you don't mind a workout). Add about a quarter of the egg mix to the dough, and whisk on medium-low speed for 20-30 seconds until the egg has incorporated. After this, add the egg a little at a time, mixing for 20-30 seconds until fully incorporated, scrape the bowl and check the consistency of the dough after each addition. The choux pastry should become smooth and shiny, and, when you lift it with a rubber spatula and let it fall back into the bowl, it should fall off slowly in a continuous ribbon, then taper off leaving a smooth V shape behind. The pastry should still be thick enough that it holds shape when it falls back into the bowl, instead of just dissolving back in. As soon as you reach this consistency, stop adding more egg. I usually have just a little bit left over, but sometimes have had to add a little more egg beyond the 4 eggs too - so it's all about the consistency! 
7. Transfer the choux pastry to a piping bag with a 1/2" round tip. You may have to pipe in batches depending on the size of your piping bags
8. Use a little choux pastry to stick the corners of the parchment paper to the baking sheet so it doesn't move as you pipe. Now pipe the choux pastry using the circle markings you made earlier. Hold the piping bag vertically, apply steady pressure and lift the piping bag up as you pipe so each mound is tall instead of flat. Once the dollop approaches the 1.5" circle marking, release pressure, lift and flick the piping bag. If piping in batches, keep the rest of the choux pastry covered or in a piping bag at room temperature
9. Take the craquelin out of the fridge/freezer. It should be firm now. Remove the parchment paper on top, and use the same piping tip as in step 1 to cut the craquelin into 1.5" discs. Cover each choux pastry dollop with a craquelin disc. If piping / baking in batches, keep the craquelin discs in the fridge so they don't become soft
10. Now, it's time to bake! Transfer the baking sheet with choux pastry piped on it into the oven. Bake at 390F for 10 minutes, then reduce the temperature to 355F without opening the oven, and bake for another 18-20 minutes until the shells are golden brown and crispy. I recommend baking on only one rack in the oven to ensure all choux buns rise evenly - and yes, this does mean you typically have to bake in batches
11. Remove from the oven, and immediately puncture holes on the bottom of each choux bun using a bismark piping tip so the steam can escape and the shells don't become soft. You will use the same holes to pipe into them later
12. Repeat until all the choux buns have been baked and cooled down

Cheesecake whipped cream:

1. Add the cream cheese, sugar, vanilla and salt to a large bowl, and whisk for 2 minutes until the mixture is creamy
2. Add the cold heavy cream, and whisk again for a few minutes until the mixture becomes thick, fluffy and holds shape (medium stiff peak consistency). Do not overmix
3. Transfer to a large piping bag in batches, and use a small round piping tip to fill each choux bun generously until the cream starts to push back
4. Dust the cream puffs with icing sugar, serve and enjoy!