Flavoured oils come in many shapes and tastes: basil, mint, chili, garlic, chili-garlic, ginger... The imagination seems to be the limit, but the store bought ones seem a bit, well, flat, oftentimes, and they usually only come in quantities that they either go bad before they are used up, or get stale and boring toward the end as they have been left open for so long. So, why not make your own? Good thing that you asked that, because that is exactly what I planned on doing.
The spices are roasted in the oven until crisp and flavourful. And just because spices are really beautiful, here are a couple of gratuitous closeups of the interesting spice landscape.
After roasting, the spices are ground to help extract flavour from them in the oil. Grounding the chili spices has to be the most sneeze-inducing thing I have ever done in my life.
The spice mix is put into a vacuum bag, the oil is added and it is cooked sous vide for 8 hours at 70°C to pasteurise the oil and the spice mix. Sealing it in using a simple home vacuum sealer is impossible as it would just suck up the oil (unless you use some clever multi-bag tricks to avoid leakage), so instead I used water to displace the air out of the bag, but none of our pots were big enough to fit the entire spice-oil mix, so finally we had to use my daughter's bathtub to get enough water depth (long live practical solutions). Cooking it sous vide at this temperature makes the oil keep a lot longer than it normally does when not cooking it. It is then stored in the fridge for another 12 hours to allow the flavours to really develop in the oil.
The vacuum bags are highly glossy so it proved impossible to take a photo without a lot of highlights. It is then strained through a cheese cloth and nicely bottled up.
I tried to show that the oil is, in reality, entirely transparent and light in colour, but despite my best efforts it looks a bit murky in the shot here. After being bottled, I tried a bit of it on its own on a tea spoon (perhaps a quarter of a tea spoon). The taste started as "oh, this is quite pleasant", "why, this has a bit of a hot aftertaste, but not too bad", "air, I need air". It is, indeed, incredibly hot, and a few drops of it suffices to make your entire dish pleasantly spicy. This size batch of chili oil is much too much for a single family to consume all by itself, unless you really love spicy food, but as a benefit, you can bottle it up in small bottles (remember to soak them in boiling water to kill any bacteria first) and give them as gifts to friends and family.