Burnt outside, raw inside

What is happening

The defining failure of a fast, small-chambered appliance, and it is a gradient problem rather than a time problem. Adding time to a set-point that is already too high makes the outside worse without helping the inside much.

Narrow it down

Each of these has an answer you already know, and each one rules something out.

1. Did the food go in frozen?

   • Yes
   • No

2. Was it coated in anything sweet — barbecue sauce, honey, a marinade?

   • Yes
   • No

Why it happens

Commonest first. It is almost always the boring one, and a page that walks you through the exotic causes before the obvious one has given you a longer path to a fixed dinner.

1. Most common

   The temperature is set too high for the thickness of the food

   Heat enters from the surface and travels inward slowly. A high set point makes the surface climb quickly and steepens the gradient across the food, so the outside reaches its finishing point long before the centre has warmed.

   What to do

   • Drop the temperature by 15–20°C and add time

2. Common

   The food went in frozen

   A frozen centre absorbs a great deal of energy simply thawing before its temperature begins to rise at all. The surface, already thawed, carries on cooking throughout.

   What to do

   • Drop the temperature by 15–20°C and add time
   • Thaw in the fridge first

3. Common

   The pieces are too thick or too uneven

   The time needed rises sharply with thickness, and an uneven piece has a thin end that finishes while the thick end is still climbing.

   What to do

   • Cut the pieces smaller
   • Even out the thickness before cooking

4. Occasional

   A sugary marinade or sauce was applied before cooking

   Sugars brown and then burn at temperatures well below those needed to cook meat through, so the coating is finished long before the food is.

   What to do

   • Add sweet sauces at the end

The fixes in full

Drop the temperature by 15–20°C and add time

A shallower gradient lets the centre catch up before the surface passes the point of no return. For cooking from frozen this is the single most useful adjustment there is.

Trade-off: Less browning, and a longer wait.

You will know it worked when: The centre reaches temperature while the surface is still golden rather than dark.

Thaw in the fridge first

For anything raw and thick — a chicken breast, a burger, a piece of fish — thawing overnight in the fridge removes the problem entirely and lets you use the fresh cooking figures.

Trade-off: Requires planning ahead.

Cut the pieces smaller

Thickness dominates cooking time. Halving the thickness helps far more than doubling the time does.

Even out the thickness before cooking

Flatten the thick end of a tapering piece, or fold a thin end under. A piece of even thickness finishes all at once, which is the only way to avoid overcooking part of it.

You will know it worked when: No part of the piece is more than about a third thicker than any other.

Add sweet sauces at the end

Cook the food plain, then toss it in sauce in the last two or three minutes, or after it comes out. Applies to barbecue sauces, honey glazes and most marinades.

You will know it worked when: The coating is glossy rather than blackened.

Evidence and confidence

Foods this affects

• Chicken breast
• Sausages
• Potato wedges

Equipment that bears on this

• Instant-read thermometer — Worth owning before anything else — The only accessory that changes what you can do rather than how comfortably you do it, and it costs less than a delivery.

Related problems

• Food cooks unevenly