Slice the onion thinly. Defrost the frozen pumpkin and cut into bite-sized pieces. Separate the broccoli into florets.

Place broccoli in a microwave-safe container, cover loosely with plastic wrap, and microwave at 600W for 1 minute. Drain excess water.

Cut the salmon into bite-sized pieces. Season with salt and pepper, then coat with 1 tbsp of flour.

Heat olive oil in a pan over medium heat. Add salmon and cook until browned. Add onion and sauté until coated with oil. Add butter and remaining flour, stirring until flour is no longer visible.

Gradually add water, stirring after each addition. Once boiling, cover and simmer on low heat for 8 minutes. Add milk, salt, and black pepper, and cook over medium heat until thickened.