Pasta with Fennel & Orange Zest

I've never made anything with fennel before so when I got some, pasta was the simplest thing that came to mind to experiment with.

For the White Sauce:
2-3 tbsps butter
2-3 tbsps flour
500 ml milk
Seasoning

In a saucepan, melt the butter, and add the flour. once blended, add the milk and keep the heat to a medium. Stir so that the lumps dissolve. Let the milk heat but not boil. Keep on low-medium heat till it thickens.
Add more flour if needed. Once done, add seasoning and keep aside.

Veggies:
2 bulbs of fennel
2 cloves Garlic
1 small onion
2 tbsp oil
Zest of 1 orange
seasoning

Separate the stem from the leaves of the fennel. Pry apart each layer of the fennel and clean thoroughly. Slice the fennel stem. Heat the oil and add the garlic. Then add the onion and fennel stems. Cook till they're soft. Then add the zest and seasoning. Lastly, add the chopped fennel leaves.

Remove from heat and mix with the white sauce. Pour this over a bed of pasta and serve!