Roasted San Marzano tomato soup

Water in the pan holds the temperature at 100 °C. At 100 °C the paste only stews.

In fat the paste gets hotter than 100 °C. Its sugars and amino acids then brown in the Maillard reaction. The raw metallic taste goes.

Use liquid only after the paste has browned. It lifts the brown layer off the pan. Each time the liquid reduces and the paste sticks again, one more brown layer forms.

Tomato holds much free glutamate. Fish sauce adds inosinate. Inosinate makes the tongue respond to glutamate much more strongly than glutamate alone. MSG adds more glutamate.

The soup tastes savoury with less added salt.

This is monter au beurre: cold butter added at the end of a sauce. Beurre monté is a different thing. It is a butter emulsion used to poach.

Butter is an emulsion. Its milk proteins and phospholipids help hold its fat in the soup. The gelatinised starch from the bread also makes the emulsion more stable. The blender makes smaller fat drops than a whisk, so the emulsion is finer.

A boil after this step breaks the emulsion and the fat separates.

Cooking removes the green, fresh aroma compounds of tomato. One raw tomato blended in at the end puts them back. The browned solids give depth and the raw tomato gives the top note.

The smoke compounds and the capsaicin of chipotle dissolve in fat, not in water. The red pigment of tomato does the same. Blooming the chipotle in the fat spreads it through the whole soup. The finishing oil and butter keep these compounds in the soup.