French toast is bread soaked in a custard of eggs and dairy, then cooked in butter until golden. The foundational ratio is 1 large egg to 60 ml (¼ cup) whole milk or cream per slice of bread — roughly 4 eggs and 240 ml dairy for 4 thick slices. Soak sturdy bread in this custard for 30 seconds per side for fresh brioche, 2–3 minutes per side for stale country bread, and up to 5 minutes for a very dense, day-old pullman loaf. The custard should penetrate to the centre without turning the bread to mush. This is where the dish lives or dies: insufficient soaking produces dry, eggy toast with a custardy skin and a bread-tasting core; excessive soaking disintegrates the bread into a soggy mass that falls apart in the pan. The bread selection is half the battle. A dense, enriched bread — brioche, challah, shokupan (Japanese milk bread), or pain de mie — absorbs custard evenly because its tight, butter-enriched crumb has small, uniform air pockets. Sourdough or open-crumbed artisan bread has large, irregular holes that flood unevenly, leaving some bites saturated and others dry. Staleness is an asset: bread that is one to two days old has lost surface moisture, which means it absorbs custard more eagerly and holds its structure better during cooking. If using fresh bread, dry slices in a 120°C (250°F) oven for 10 minutes to drive off surface moisture before soaking. The custard itself rewards precision. Whole eggs provide structure (the proteins set during cooking, firming the exterior), while the dairy contributes richness and moderates the egg flavour. Heavy cream (35% fat) produces the richest result; whole milk (3.5% fat) is lighter and lets the bread flavour come through. A tablespoon of sugar per two eggs adds sweetness to the custard itself rather than relying solely on toppings. Vanilla extract (5 ml per batch), a pinch of nutmeg, and a pinch of cinnamon are the classic aromatics, though orange zest and a tablespoon of Grand Marnier move the dish toward the French pain perdu tradition. Whisk the custard thoroughly — any unincorporated egg white leaves slimy, translucent patches on the finished toast. Cook in a blend of butter and neutral oil (half and half) over medium heat — 150°C (300°F) on the surface. Pure butter burns before the custard sets; pure oil lacks flavour. When the butter foams and the foam subsides, lay in the soaked bread. Cook for 2.5–3 minutes per side. The Maillard reaction between the egg proteins and the milk sugars produces the deep golden-brown crust that defines great French toast. Do not press the bread down — compression squeezes out the custard you spent minutes infusing. The quality hierarchy: (1) A competent French toast is cooked through, evenly browned, and custardy. (2) A great French toast has a caramelised, almost crackling exterior with a rich custard interior that is fully set but still moist — cut into it and it should look like a cross between bread pudding and crème brûlée. (3) A transcendent French toast uses thick-cut (3 cm / 1.25 inch) day-old brioche, soaked in a custard enriched with heavy cream and a tablespoon of crème fraîche, cooked slowly in brown butter until the surface is the colour of aged mahogany, finished for 5 minutes in a 180°C (350°F) oven to set the centre, then dusted with powdered sugar that melts into a glaze on contact. Sensory tests: press the centre gently with a fingertip. A properly cooked French toast yields slightly and springs back — the custard is set. If your finger leaves a permanent dent, the centre is still liquid. The aroma should be butter-forward with vanilla and caramel notes. A sulphurous or strongly eggy smell indicates too much egg relative to dairy, or insufficient cooking.
The egg-to-dairy ratio governs texture. More egg produces a firmer, denser custard that can veer into omelette territory. More dairy produces a softer, more delicate interior but risks the bread disintegrating during soaking. The 1:1 ratio by volume (one egg weighs roughly 50 g; 60 ml of milk weighs roughly 60 g) is the baseline. For a richer result, replace half the milk with heavy cream. For a lighter result, add a tablespoon of milk per egg. Bread thickness determines soaking time and cooking method. Thin slices (1 cm) need only a brief dip — 15 seconds per side — and cook entirely on the stovetop. Thick slices (3 cm or more) require extended soaking and benefit from a stovetop-to-oven approach: sear both sides for colour and crust, then transfer to a 180°C (350°F) oven for 5–8 minutes to set the interior without burning the exterior. The custard must be at room temperature. Cold custard straight from the refrigerator drops the pan temperature on contact, extending cooking time and producing uneven browning.
For the ultimate brunch French toast, make it the night before: soak thick-cut brioche in custard, arrange in a buttered baking dish, cover, and refrigerate overnight. In the morning, bake at 190°C (375°F) for 25–30 minutes until puffed and golden — no stovetop required, and the long soak guarantees full custard penetration. For a savoury version, omit the sugar, vanilla, and cinnamon, and add 30 g grated Gruyère, a pinch of white pepper, and a teaspoon of Dijon mustard to the custard — this is essentially a croque monsieur without the béchamel. For pain perdu in the true French tradition, use a stale baguette cut on the bias into 4 cm slices, soak for 5 minutes, and fry in clarified butter until deeply caramelised, then finish with a spoonful of salted caramel and a pinch of fleur de sel.
Using sandwich bread — it is too thin, too soft, and dissolves on contact with the custard. Second: soaking too briefly, which leaves a dry, bready centre that tastes like warm toast with an egg coating rather than a unified custard-bread entity. Third: too-high heat, which scorches the exterior while the centre remains raw custard — the egg proteins on the surface caramelise and burn before the interior sets. Fourth: not whisking the custard thoroughly, leaving streaks of egg white that cook into translucent, rubbery patches. Strain through a fine-mesh sieve if necessary. Fifth: cooking in butter alone over medium-high heat — butter's milk solids burn at 150°C (302°F), exactly the temperature you need for proper browning. Clarified butter or a butter-oil blend solves this.