What, if any, is the difference between chilli powder, chilli flakes, hot paprika and cayenne pepper, and can any of these be used as a substitute for fresh chilli peppers in recipes?

Chilli powder, invented in Texas, is a mixture of powdered red chillies (often cayenne peppers), cumin, oregano, garlic powder and salt. It is perfect for flavouring beef or turkey chilli and other Mexican dishes, but not suitable for authentic Indian or Chinese dishes. In good spice merchants, you can also find pure powdered chilli, which will specify the type of chillies used: ancho (rich and fruity), chipotle (pronounced chi-pot-lay; sweet and smokey) or kashmiri (warm and vibrant).

Chilli comes in myriad forms, from fresh (above) to hot paprika and cayenne pepper. But which to use?

Chilli flakes are simply crushed, dried red chillies. Since it contains some seeds and is undiluted by other ingredients, chilli flakes tend to be much hotter than chilli powder.

Hungarian hot paprika or Erös tastes of sweet peppers but with a definite kick. It is typically made from dried cherry peppers, and is light brown in colour. Don't confuse it with Spanish hot smoked paprika, which has a distinctive, smoky flavour.

Finally, cayenne pepper, named after the city in French Guiana, is a hot, though not particularly flavourful, powder of ground chillies. It adds heat though little flavour or complexity.

If a recipe calls for fresh red chillies, you can generally substitute chilli flakes or small whole dried chillies and a small quantity of sweet red peppers, although the flavour will not be quite the same. Fresh green chillies have a piquancy and freshness that's hard to replicate, but a teaspoon of dried jalapeno flakes is a respectable alternative.

I like to bake my own challah. I take it out when the outside is very brown, but when I cut into it the inside is often doughy and under-cooked. What am I doing wrong?

A well-done exterior and undercooked interior can be a sign that the oven is too hot. While challah, like all breads, needs to go into a very hot oven (230°C, gas 8), it should be turned down to 200°C (gas 6) once the loaf is in the oven. It is ready when an instant-read thermometer inserted into the side of the loaf reads about 86°C. If the bread is brown but not at the correct internal temperature, reduce the heat to 190°C (gas 5) and continue baking until done.

Some older ovens can "run hot", so it is a good idea to check the actual temperature with a good oven thermometer; in addition, there can be a significant temperature difference between the top and bottom of the oven, so it is best to bake bread (and cakes) in the lower middle position.

I'd like to buy some good-quality kitchen knives. What is the best way to keep them sharp, and how often should I use a sharpener?

A knife is like a pair of shoes. It should feel really comfortable to hold, well-balanced and natural to use. So always try before you buy. Good-quality, durable knives have forged rather than stamped blades. European-made knives tend to have thicker, heavier blades than Japanese knives which are lighter, thinner and sometimes sharper (think Samurai sword versus Medieval broad-sword).

Always store your knives in a block or on a magnetic rack, never in a drawer (which is bad for the knives as well as fingers). Second, never put them in the dishwasher (very bad for knives and dishwashers). And third, never cut on very hard surfaces like granite, marble or glass - they will dull the blade in no time and quite possibly damage it.

To keep that really sharp edge on your knives, you'll need to hone them regularly (once or twice a week, depending on both the knife and your use). Honing it not the same as sharpening. Honing, which is done using a poker-like honing steel (sometimes confusingly called a "sharpening steel") aligns the micro-serrations along the edge of the blade, straightening out the wear caused by the cutting action. They are really easy to use, and once you know how, make a world of difference to how well a knife cuts, and how long it will last between sharpenings.

After several months of use and regular honing, knives will need sharpening to reshape (rather than realign) the edge by shaving off a small amount of metal. Sharpening too often or too aggressively can damage the blade and shorten the life of your knife, so professional chefs hone their knives every day but have them sharpened by a master knife-sharpener once or twice a year.

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