Spray 13x9 baking dish. Preheat oven to 375. Thinly sliced potatoes.
Dice onions.
Cube cheese block.
Melt butter in medium sauce pan on medium heat.
On medium high heat in medium skillet cook ground beef until browned and crumbled. Set aside.
Add diced onions to melted butter and cook until translucent (about 3 minutes).
Add corn starch and dried thyme. Cook an additional 1 minute while stirring well.
Add 2 cups broth. Stir continuously until thickened. (3-5 minutes)
Add other cup of broth. Stir well. Reduce temp to medium-low.
Add sour cream. Stir until smooth and well incorporated.
Add Colby jack cheese. Stir continuously until melted and incorporated into sauce. Remove from heat.
Spread half of potatoes in bottom of baking dish. Sprinkle with salt and pepper.
Top potatoes with cooked ground beef.
Layer the rest of the potatoes on top of the ground beef. Salt and pepper.
Pour the cheese sauce over the potatoes and ground beef layers.
Wrap tightly with aluminum foil. Set baking dish on a baking pan to collect any spillover. Bake for 45 minutes.
After 45 minutes, remove foil. Add 1 cup shredded cheddar.
Add 1 cup Italian bread crumbs. Return to oven uncovered additional 15 minutes.
Remove from oven and let rest 15-20 minutes before serving.
