All-American Cheesesteak with Horseradish Sauce

yellow onion, cut in half and sliced

cremini mushrooms, sliced

dried thyme

boneless ribeye steak, sliced thinly and then chopped

slices provolone cheese

butter, divided

salt and pepper

hoagie rolls

mayo

prepared horseradish

garlic, grated or pressed through garlic press

granulated sugar

salt, or more, to your tastes

black pepper, or more, to your tastes