Quinoa and Broccoli Casserole (Good Eats Style)

Alton Brown is 2 for 2 in the fall 2019 season of Good Eats! I've been looking for more dishes that expand our breadth of proteins and leverage more vegetables. This dish fit the bill perfectly — with a few alterations to match a family of four's appetite.

• 3/4 c quinoa (rinsed)
• 1 1/2 c chicken stock
• 2 tsp kosher salt (in two 1 tsp portions)
• 1 medium crown broccoli (florets cut and broken into small pieces)
• 4 oz crimini mushrooms (sliced)
• 2 tbsp butter (in two 1 tbsp portions)
• 1 small onion (fine dice)
• 1 tbsp mustard seed (ground)
• 1/2 tsp smoked paprika
• 1/4 tsp black pepper (ground)
• 1/8 tsp white pepper
• dash of cayenne pepper (ground)
• 1 1/2 c half-and-half
• 1 egg (beaten)
• 8 oz sharp cheddar cheese (coarse shred)
• 1/4 c mayonaise