Reuben Sandwich with homemade mayonnaise

👨‍🍳 Method

For the Hot Sandwich

1. 1
   Spread the butter on the outside of slice the bread.

   💡The butter goes on the outside, the side that meets the pan: it's what gives the bread its golden, crisp crust.
2. 2
   Put the egg, mustard, salt and black pepper in the blender jar and blend about half a minute.

   BlenderorStick blenderorFood processor
3. 3
   Add the oil in a thin, slow stream, while the blender is running, until a thick emulsion forms.

   Blender

   💡The thin stream is everything: fat that goes in too fast can't bind, and the sauce breaks. For mayonnaise and hollandaise, if this happens, start with a fresh yolk and slowly add the broken sauce to it; if the sauce is too thick, thin it with a teaspoon of water.
4. 4
   Add the lemon juice and stir. Taste and adjust the seasoning.
5. 5
   Mix the mayonnaise and tomato paste into a sauce and spread it on the inside of slice the bread.
6. 6
   Place the yellow cheese, meat and sauerkraut on half of slice the bread and cover each one with another slice, buttered side out.
7. 7
   Heat a heavy pan over medium heat.

   StoveFrying pan
8. 8
   Grill the sandwiches 3 minutes per side, until the bread is golden and crisp and the cheese has melted completely.

   StoveFrying panSilicone spatula

   💡Medium heat, not high: the bread browns at the same pace the cheese melts, while over high heat it burns outside before the cheese inside melts.
9. 9
   Cut on the diagonal.

   KnifeCutting board