Take the heavy bottom steel cooking pan. Melt butter in it over medium heat.
Once the butter is melted, add all purpose flour to the pan and mix it well using a wire whisk. Cook it on medium heat for 3 minutes while mixing it continuously. Refer to the video above.
Now add milk to the pan, 1 cup at a time and keep stirring. Stir quickly so that no lumps are formed. Refer to the video above. Keep the heat on the stove at medium the whole time. Cook the sauce till it thickens slightly.
Add salt, black pepper powder and mustard sauce to the pan and give a good mix to it. Now add cheese to the sauce, little bit at a time. Keep mixing with the wire whisk to mix well.
Keep the heat at medium-low until cheese is melted well. Switch off the heat.
Now add boiled and drained pasta to the cheesy bechamel sauce. Mix pasta and sauce well.
Your Panera Bread Style Mac n Cheese is ready. Serve it warm. You can add dried parsley or basil or any other seasoning of your choice for more flavor. But you can not beat the classic Mac n cheese.