Is there a way to understand when the cake is cooked without inserting a knife/skewer into the cake?

Some light cakes you can understand by pressing with your fingers and seeing if it bounces back, but for heavy, rich fruit cakes, the knife or the skewer way is the best.

Can I make meat/vegetable stock in large quantities and store it in the fridge?

Best you reduce it down to make a concentrate that you can then freeze in pouches or containers. Even easier with meat and fish concentrates as it will turn into jelly once chilled. 

While cooking octopus at home, it becomes very rubbery. What is the right way to cook octopus so that it stays tender?

I love octopus! Where did you get it? Did you just come back from Spain? Are you an octopus dealer? Will you be my supplier? Is this just an attempt at making yourself sound epicurious? 

Anyway simmer it for about an hour in water with a whole onion, carrot, celery sticks and some garlic, salt and pepper until it’s tender. You can then cut it up and grill it, make a great curry with it but if you ask me then saute in butter with garlic, lemon, chilli flakes and lots of parsley.

(PS: This t2 girl picked up octopus from Metro Cash & Carry.) 

How can I plate curry dishes nicely to make the dish look appetising?

I’d have to write a book for you! Meanwhile, get yourself on Pinterest.com like everyone else and get those creative juices flowing!

Chefs don’t tell customers that gelatin is completely non-vegetarian since it’s made from the skin and cartilage of animals. How do you substitute it with agar-agar?

I’m pretty much sure that all of my vegetarian friends know that gelatin is non-vegetarian but a bit like the egg saga in cakes, for most, if they’ve not asked then they can carry on chomping!

You can always replace gelatin with agar-agar but they’re both completely different. Gelatin will always melt and give you that great mouth feel but agar-agar will never. I don’t really like that rubbery texture. A bit like the difference between butter and margarine. The rest I’ll leave to you.

Why does my chocolate or plain vanilla sponge always crack down the middle in the oven?

If it’s a beaten mixture, this usually happens. If it calls for a folding method, you’ll need to treat it like a lady and fold the flour in lightly. 
(Please note: This is no place to take out your sexual and or other personal frustrations with that spatula!) 

How long should I marinate bekti or pomfret for fry and chicken for grilling? 

How long’s a piece of string?! Each to his own.

Is there an alternative to using a blowtorch for caramelising sugar for a creme brulee?

If you have an overhead griller or salamander, as we call them in the industry, crank it up to full power and do it the old-fashioned way.

Is truffle oil desirable in 2017 since it’s a big hocus-pocus that’s created in labs and mixed with olive oil and chemical compounds?

Ooooo someone’s done their homework today! Well done! Did you just copy/paste that from the Internet? Like anything else, a lot is crap, yes, but if you’re lucky enough to find yourself a bottle of natural white truffle oil, a drizzle on your porcini pasta or a whole baked lobster will fill the room with such an intense fragrance and have the hairs standing up on the back of your neck and over a glass of wine or two with a loved one you might get lucky tonight and much better than wasting all that time copying things from the Internet!

Do flavoured oils like garlic/chilli oil help enhance the taste of the dish? How easy or hard is it to make them?

They look pretty I suppose and can enhance flavours if used properly. Spice oils are great! But there are different ways to get those colours and flavours depending on what you want. I’ll give you a couple to get you started and the rest you can make up as you go along…

Spice: Roast whole first and slowly heat in the oil for 20 minutes or so.
Garlic: Slowly simmer whole cloves of garlic in the oil until they turn that delicious golden colour, again for around 15 minutes (slowly!).
Chilli: Simmer Kashmiri dry red chillies in a little water for half an hour first to draw out the colour until there is hardly any water left. Then blend them with oil and drip it through a coffee filter. 
Herb: Place fresh herbs into a blender and blend well with warmed oil then again drip through a coffee filter. The oil and water from the herbs will eventually separate so you can skim off the oil. 

Would you recommend salting eggs while scrambling them or after?

For scrambles and omelettes, always salt eggs afterwards. Salting before will break down the structure of the egg and make it watery.