Marble onion rye bread

Scald the milk in a saucepan: heat it over low until just under a simmer and hold it there 30 seconds to a minute, moderating the heat so it does not boil. This destroys enzymes that inhibit gluten formation and increases the bread's capacity to hold moisture.

Make two dry mixes, each equal amounts of bread flour and rye flour - light rye in one, dark rye in the other.

Add one tablespoon of cocoa powder to the dark mix; it is only for the colour and is not tasted in the finished dough.

Add two teaspoons of caraway seeds, half a teaspoon of instant yeast and five grams of kosher salt to each mix.

Off the heat, stir the two tablespoons of oil and the molasses into the scalded milk, then half a cup of cold water to bring the temperature down.

Cool the liquid to 110F before it goes near the yeast; above about 110F risks killing it. At 130F it still needs another five or 10 degrees.

Weigh the liquid and divide it evenly between the two bowls, about 200 grams each.

Combine wet into dry with a bowl scraper, turn out and work by hand, adding extra bread flour if it is sticky. It should be a firm dough.

Flatten each dough out, scatter about three tablespoons of chopped onion over it and fold the dough up and around; add a little more flour as the onion releases moisture.

Knead about five more minutes until smooth, firm, elastic and well developed - poked, it should contract and spring back.

Divide each dough in half for four pieces in all, form each into a sphere, oil them and the bowl, cover and rise together until about doubled - about an hour in a warm kitchen, a couple of hours in a cold one.

Oil a standard loaf pan and coat the bottom and all four sides generously with coarse ground cornmeal to stop the loaf sticking.

Pat and roll each piece out to a roughly square shape about the width of the pan; patting also degases the dough and brings the yeast into contact with new food for the second rise.

Stack the sheets light, dark, light, dark.

Roll the stack up onto itself with a little flour on the surface, stretching the dough over itself to create tension, pinch the ends together and rest it on its seam.

Set it seam down in the prepared pan and press it to fill the pan. Cover and refrigerate to rise slowly overnight.

Bring it back to room temperature until domed and rising about an inch out of the pan. A split side after baking means it was under-proofed.

Brush the top with a bit of heavy cream - an egg wash or milk also works - and sprinkle with flaky salt.

Bake at 350F for 50 to 60 minutes, until the internal temperature at the tallest part of the centre is 190F; anywhere between 190 and 200 is fine. Visual indicators will not tell you.

Cool in the pan. The escaping steam softens the crust, which is nicer for sandwiches, and helps the loaf pull away from the sides. Cut round the sides and turn it out.

Slice about half an inch thick.

Build a corned beef sandwich: Russian dressing on one slice, spicy brown mustard on the other, sauerkraut on the mustard side and warmed corned beef between.