Combine milk, butter, salt, mustard, pepper and cayenne in a medium-sized saucepan; bring to a boil.

Remove from heat; beat in flour all at once and stir until mixture forms a ball of dough.

Return to medium heat; cook a few minutes longer scraping mixture along the bottom of pot to dry dough slightly.

Transfer dough to a bowl; cool 5 minutes.

Beat in three eggs, one at a time. Mixture will be slippery.

Beat the fourth egg lightly and reserve 2 tbsp egg with 1 tbsp milk. Beat remaining egg into dough.

Add both cheeses; combine well.

Butter a cookie sheet; dust lightly with flour; trace out an 8" circle.

Spoon batter in mounds around the outside edge of circle; mounds should barely touch each other.

Brush tops with egg-milk mixture; sprinkle with sesame seeds.

Bake in a pre-heated oven at 425°F for 10 min. Reduce heat to 350°F, continue to bake 45 to 55 min. longer or until biscuits are firm and golden.

Serve warm.