Jambon-beurre (Ham and Butter Baguette)

Variations

• Jambon-beurre-cornichon: with cornichons inside. Sold nearly as often in French bakeries; the acid and the crunch cut the fat. It is the one addition this recipe allows.
• Jambon-fromage, or a parisien: with a slice of emmental or comte added. That the name changes is the point — a jambon-beurre is close to being defined by what is not added to it.
• Beurre demi-sel: Breton salted butter. Use one with salt crystals you can feel and no further seasoning is needed; it is effectively the standard here (butter).
• Changing the bread: a baguette tradition, thick-crusted and open-crumbed, is the reference for this job. Enriched bread like brioche buries the butter layer, and a country loaf has a crust chewy enough that the filling pulls out in one bite (baguette).
• Changing the ham: dry-cured ham instead of jambon is much saltier and wants less butter. Smoked ham puts an aroma over the butter rather than beside it.
• Its descendant in Vietnam: banh mi is directly this sandwich. On the baguette the French left behind, pate and mayonnaise took the butter's place, with coriander and pickled vegetables, and it became something else entirely.
• The hot versions: the same ham and bread make a croque monsieur and a grilled cheese. Only the jambon-beurre uses no heat at all.
• Same discipline elsewhere: Japan's tamago sando also strips a sandwich down and does one thing exactly.
• The rest of the morning: croissants and pain au chocolat, omelette and quiche, from the same bakery and the same table.

Tips

• The bread is more than half the dish, by weight and by flavour. With three ingredients, the condition of the largest one is the result. A jambon-beurre built on yesterday's baguette cannot be rescued by anything done to it afterwards.
• The butter is an ingredient, not a condiment. 20-30g per sandwich, three or four times what goes on a slice of toast. Spread thin it becomes a ham sandwich, and half the name of the dish disappears (dairy and heat).
• The butter is also waterproofing. Taken edge to edge on both faces, it keeps the ham's moisture out of the crumb, so the sandwich is still good hours later. That is why it survived as picnic food.
• With salted butter, add no salt. All the seasoning here is the salt in the butter and the cure in the ham, which is why unsalted butter leaves it flat (salt and seasoning).
• Fold the ham. Flat versus folded is the whole difference in texture. A few slices of a decent thickness beat many thin ones.
• Leave a hinge when you cut. Split into two separate halves, the top and bottom slide apart as you eat and the filling is pushed out. Attached along one edge, it folds and holds (knife skills).
• Let it cool before buttering. A baguette straight from the oven is tempting and will absorb every gram of it. Five minutes of cooling also crisps the crust further (what your oven is doing).
• Do not skip the wrapped ten minutes. Straight after building, the butter reads as lumps; ten minutes later it reads as a layer. In a recipe with almost no cooking time, that interval is the cooking.
• Do not eat it cold. Fridge butter is waxy, and bread stales fastest at refrigerator temperature. If it has to be made ahead, wrapped in paper at room temperature is better (serving temperature).
• Freezing the baguette does work. Halve it the day you buy it, freeze it, and bake it from frozen at 200C for 8-10 minutes; it comes back close to same-day. It is one of the few things that takes freezing badly but refrigeration worse (freezing and thawing).
• It is the best-selling sandwich in France, by a wide margin and in the billions per year, and a "jambon-beurre index" comparing city prices makes the papers annually. It survived not because it is simple but because three ingredients show their quality with nothing to hide behind.
• If you bake the bread yourself, aim for a thick crust and a holey crumb: a wet dough and a long ferment get you there, and the highest-protein flour is not required (dough and gluten, choosing flour).