Buttering and flouring a mould
chemisage
Chemisage is a way of preparing a mould: the surface is first coated with softened butter, then dusted with flour and the excess knocked out. The result is a thin release film along which the baked item comes free of the walls.
The mechanism is simple. The fat stops the batter sticking, while the flour absorbs part of the fat and forms a dry layer that does not dissolve under heat. Butter alone is usually not enough — it melts and runs, leaving the walls bare.
Apply the butter with a soft brush, and in strictly vertical strokes if the item has to rise: horizontal strokes leave ridges that a soufflé catches on unevenly, and it climbs crooked.
Other dustings replace flour depending on the item: sugar for ramekins holding soufflé and crème brûlée, cocoa for chocolate cakes so no white film shows, ground nuts or semolina.
For moulds with intricate relief, spray release or silicone is more reliable — chemisage settles unevenly in deep recesses.