2 tbsp (25 mL) water
1/4 cup (50 mL) dry bread crumbs
1 small onion, grated
2 tsp (10 mL) dijon mustard
1/2 tsp (2 mL) each dried thyme and salt
1/4 tsp (1 mL) pepper
1 lb (500 g) lean ground beef
1/2 cup (125 mL) shredded aged cheddar cheese
4 hamburger buns
In large bowl, beat egg with water; stir in bread crumbs, onion, Dijon mustard, thyme, salt and pepper. Add beef; mix just until combined.
Divide into quarters; shape into balls. With finger, make well in each ball; place one-quarter of the cheese in well. Press meat over to enclose cheese. Press into four 3/4-inch (2 cm) thick patties. (Make-ahead: Layer between waxed paper in airtight container and refrigerate for up to 24 hours or freeze for up to 1 month. Thaw in refrigerator.)
Place patties on greased grill over medium heat; close lid and grill, turning once, until digital thermometer inserted sideways into centre reads 160°F (71°C), 12 to 14 minutes. Serve on buns.