Place Krusteaz Professional Fudge Brownie Mix, water, and corn syrup in mixer bowl. Using a paddle, mix on low speed 30 seconds. If using Ready to Bake Brownie Batter, omit the water and use a spatula to stir in the corn syrup.
Scrape bowl and paddle. Continue to mix on low speed 30 seconds. Omit this step if using Ready to Bake Brownie Batter.
Using a #20 scoop, fill prepared muffin pans.
Press 1 peanut butter cup into the center of each muffin cup.
For convection oven, bake at 300°F 25-30 minutes; for standard oven, bake at 350°F 25-30 minutes.
Cool 5 minutes; remove warm brownies from pan. Drizzle with chocolate glaze and sprinkle with chopped nuts if desired.