Preheat oven to 350 degrees.

In a medium sized skillet set over medium heat add bratwursts and ½ cup water.

In a measuring cup add ¾ cup beer and set aside.

Pour the remaining of the beer in the skillet with the bratwurst.

Let the bratwurst simmer (adding more water if needed) until they are firm.

Once they are cooked let the water cook down and then brown slightly in the pan.

Once the bratwursts are fully cooked remove from the pan and set aside.

When they are cool to the touch cut in half lengthwise and then in ½ inch chunks.

Add a large pot full of water over high heat and bring to a boil.

Salt the water once boiling and add in the pasta.

Cook until al dente, drain and set aside.

In a large oven safe skillet set over medium high heat add butter.

Cook until melted and stir in garlic and saute until just fragrant.

Whisk in flour, mustard powder, kosher salt and black pepper.

Cook the flour until it's melted into the butter.

Slowly pour (while whisking) the milk and reserved ¾ cup beer into the flour mixture.

Whisk together until smooth, bring to a boil and cook until thick.

Remove from the heat and stir in 2 cups sharp cheddar cheese and pepper jack cheese.

Once fully melted stir in pasta and bratwurst and smooth out the top.

Sprinkle with remaining 1 cup shredded cheddar cheese.

In a small bowl mix together crushed pretzels and melted butter.

Top the mac and cheese with pretzels and add to the oven for 25 minutes until the top is browned and the sides are bubbly.

Serve immediately.