In a small saucepan over medium heat, heat 1 tablespoon of oil. Add 2 squeezed garlic cloves and hold for about 30 seconds until transparent. Then add crackers, mix well for about 2 minutes. Heat a large frying pan over medium heat.
Pour in olive oil. Salt and pepper the salmon fillet and put it on the heated pan with the skin up. Inverted, the fillet should be golden on the sides and slightly dull in the middle. Do not flip.
Transfer the cooked fillet to a plate, and put the remaining 1/2 tablespoonful of butter, chopped shallots, garlic and sage into the pan. Stir and cook for 2 minutes, then pour in white wine.
The sauce will boil and slightly decrease in volume. After 3 minutes, add milk and mustard. Keep the sauce 2 minutes until thickened while continuing to stir. Salt and pepper. Add some more mustard to taste.
Serve salmon in a saucepan . Sprinkle with breadcrumbs on top. Serve with rice, potatoes, vegetables or salad.