-
1
To make the topping:
-
2
Add the bread and butter into a food processer, process until coarse crumbs form.
-
3
Set aside.
-
4
To make the mac and cheese:
-
5
Bring a large pot of water to a boil.
-
6
Add the pasta and 1 1/2 teaspoons of salt, cook until the macaroni becomes tender.
-
7
Drain well in the colander and set aside.
-
8
In the same pot, heat the butter over medium-high heat until butter is foaming.
-
9
Add the onion, stirring often, and cook until the onions start to brown, 5 to 7 minutes.
-
10
Whisk in the flour, and cook until the color of the mixture is very dark and smells very fragrant.
-
11
Slowly whisk in the milk, then bring the mixture to a full boil to thick up, whisking constantly to ensure a smooth sauce.
-
12
Place the oven rack to lower-middle postion and preheat the broiler.
-
13
Reduce the heat to medium or medium low and maintain a gentle simmer, whisking often, until the sauce has thickened like heavy cream, 4 to 6 minutes.
-
14
Remove the pot from the heat, add the sausages, whole grain mustard, cheeses and up to 1/2 teaspoon of salt or to taste (we omit the salt), whisking constantly until the cheeses are completely melted.
-
15
Return the macaroni to the pot with the sauce, and simmer for another 5 to 8 minutes until heated through or desired thickness is reached.
-
16
Spoon the mixture to a broiler-safe 8 by 8-inch or similar capacity casserole dish.
-
17
Sprinkle the topping mixture evenly on top.
-
18
Broil until the bread crumbs become deep golden and brown, about 4 minutes.
-
19
Rotate the baking dish half way through to ensure the topping is evenly browned.
-
20
Remove from the oven, and let cool for a few minutes.
-
21
Serve warm.
