First get your broccoli ready: wash, cut the stem ends, and cut everything into small pieces. You can leave the florets a little bigger than the stem pieces. (It also helps if you peel the lower part of the stem before chopping.)
Bring a large pot of water to a boil. Add salt and cook the pasta according to package directions.
3-4 minutes before pasta is done cooking, add the broccoli to the pasta and continue to simmer.
Drain pasta and broccoli in a colander. Return the pot to the heat.
Over medium heat, melt butter and whisk in the the flour. Keep stirring for 3-4 minutes until the mix looks puffy. Don't let it get dark.
Add the milk slowly, stirring constantly. Keep stirring for a few minutes until the sauce has thickened. Stir in cheeses, and cook over low heat until cheese is melted.
Add cooked pasta and broccoli to the sauce and adjust seasoning. If you don't want to bake your mac and cheese, you can eat it as is.
If you want to bake your mac and cheese, pour the mix into a greased baking dish.
In a small bowl, mix breadcrumbs and oil with your fingers and sprinkle over the pasta mix. Bake at 375 degree for about 20 - 30 minutes.