Make the cheese sauce by melting the butter in a medium saucepan. Whisk in the Wondra flour and cook for about 3 minutes, while continuing to whisk. Slowly add the warm milk, whisking until smooth and thick.
Strain the sauce, then add the sharp cheddar and grated Parmesan and whisk to combine. Return sauce to the pan. Set aside.
Cut a round of bread out of each slice using a shot glass or cookie/biscuit cutter.
Heat butter in a medium sauté pan. Add bread slices and bread rounds.
Break an egg into the middle of each slice of bread. Cover pan with a lid for a couple of minutes until the egg starts to set.
Remove lid and check hats to see if they're browned. When they're browned, flip all the bread to brown the other sides, adding more butter if needed.
Once the second side is browned, remove to plates, top with asparagus.
Check the cheese sauce. If it is too thick, thin with a little warm milk and reheat if necessary.
Top the asparagus with cheese sauce, more cheese, and a sprinkle of cayenne, if desired. Then perch the "hat" over the egg.
Serve immediately.
