If you increase the supply of fast food you increase competition which lowers prices so people will consume more. The economy is obviously driven by a balance between supply and demand, with prices being the mediator.
That presupposes that restaurateur was making fat profits. If he isn't, then increasing supply in the absence of higher demand will only result in the restaurant going out of business. But increasing demand will grow the economy even when the restaurateur is making thin profits.
People will not buy mud pies unless the price is so outrageously low that they can use the mud for their garden. The opposite equivalent of a mud pie is a product that nobody will produce except at an outrageously high price.
The world already has infinite demand. As in people already want to own an infinite amount of things.
I would love to own a thousand mansions. If someone were to mind control me and make it so that I doubly want more mansions, that doesn't effect at all whether those mansions exist.
People "wanting" things doesn't make them exist, because society already wants an infinite amount of things!
Suppy is the act of creating things of value. Demand is just the method of DISTRIBUTING those things of value. But at the end of the day, what matters is creation.
Your restraunt example doesn't work, because imagine if I had a magic machine that could instantly create hamburgers for free. I could easily find people in the world who currently "demand" this food, for me to give it away to.
THAT is what it means to "increase supply". Creating things more efficiently for less resources is the exact same thing as having a magic machine that creates things for free.
Or in other words, if you haven't created more things using less resources, then you haven't actually increased supply.
Demand is just the method of distributing those finite amount of goods.
Your musings about infinite demand and magic production technologies are not entirely uninteresting, but they miss a huge universe of much more interesting and immediately applicable ideas.