create: tuna pasta bake (my way)

This one is for Lise - so she can make it tonight.  And for boyfriend - because he loves it, and the photo he took was of his third serve...

About 300gm pasta spirals

1 onion, chopped

1 tbsp olive oil
About 2 - 3 tbsp butter
About 3 tbsp plain flour
500ml milk
425gm can tuna in springwater
2 tbsp wholegrain mustard
salt, pepper,
1/2 cup fresh breadcrumbs
1/2 cup grated cheese

Cook the pasta in salted boiling water.  Place in the bottom of baking dish (I use a Pyrex rectangular dish).  In saucepan, heat oil and cook onion gently until soft.  Add butter and when melted, add flour and cook, stirring, 2 minutes.  Then add milk, and stir until mixture is boils and thickens.  Add tuna, mustard (to taste) and season.   Pour sauce over pasta and sprinkle with breadcrumbs and cheese.  Bake in oven 30 minutes or until golden brown (hit it with the grill if your cheese won't brown and you can't wait any longer).