In a small saucepan, simmer maple syrup, bourbon, mustard, garlic powder, and salt over low heat for 3–4 minutes. Set aside.
Heat the shredded brisket until warmed through.
Toast waffles until golden and crispy.
Place one waffle on a surface. Layer with 2 slices of cheese, brisket, a drizzle of glaze, 2 more slices of cheese, then the second waffle.
Melt butter in a skillet over medium heat. Add the sandwich and press gently. Grill for 2–3 minutes per side until golden and melty.
Slice and serve hot, with extra glaze if desired.
Notes
Use leftover brisket for faster prep.Swap cheddar with gouda or pepper jack for variety.For alcohol-free glaze, omit bourbon or replace with apple cider.