Bring water to boil in a medium pot and salt it liberally. Blanch broccoli in the salted water for three minutes, then remove with a slotted spoon. Add the Japanese noodles to the pot and cook according to package instructions. Reserve some of the water for the sauce.

Meanwhile, season the salmon with 1/4 teaspoon salt and 1/4 teaspoon pepper. Toss in one tablespoon flour.

Heat a large frying pan over medium heat and spray with cooking spray. Cook salmon cubes for three minutes per side. Remove from pan.

Over medium-low heat, melt two tablespoons butter and add garlic. When butter is melted but not browned, add in two tablespoons flour. Whisk until all the flour is combined with the butter, then cook an additional minute. 

Add milk, yogurt, lemon juice, and mustard. Whisk until incorporated, then bring to a boil. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper, or to taste. Add in one to two tablespoons reserved pasta water to smooth out the sauce.

Stir in pasta, salmon, and broccoli. Cook all together for an additional minute or until combined.