Pesto Mac and Cheese

Some may feel that toying with a classic is aberrant, but I think this tastes pretty darned good! You can also omit the pesto just for a regular old tasty mac&cheese.

8 oz dry chunky pasta like macaroni, fusilli, etc
2 (1oz/28gr) + 2 (1oz/28gr) Tbsps butter
¾ cups (75g) panko
1 small onion (4oz/115g)
1 Tbsp flour
¼ tsp dry mustard
⅛ tsp pepper
1 tsp salt
1½ cups milk
1 cup (about 2.5 oz) grated sharp cheddar
1 cup (about 2.5 oz) grated gruyère cheese
Optional 1.5 oz chèvre cheese
2 Tbsps to ¼ cup pesto

1. Preheat oven to 350°F.
2. Boil the pasta in some salted water until just al dente; tender but firm (it will cook more when baking, and mushy pasta isn't great).
3. Meanwhile, in a hot pan, melt 2 Tbsps of the butter and mix in the breadcrumbs, stirring until evenly combined, and set aside.
4. Melt the remaining 2 Tbsps of butter and cook the onion until perfectly tender, about 5 minutes.
5. Blend in the flour, mustard, pepper and salt.
6. Stir in the milk and whisk until it thickens into a sauce. 
7. Remove for the heat source and stir in the cheese until well combined.
8. Add the pesto and combine, followed by the pasta. Mix until the pasta is uniformly covered.
9. Pour the pasta into the baking dish and sprinkle the breadcrumbs over the surface.
10. Bake in the oven for 20 minutes or until the sauce is bubbling and the top is toasted and golden.