Croque Monsieur

Melt half the butter in a saucepan over medium heat. Add the flour and cook, stirring, for 1 min or until mixture is slightly grainy. Remove from heat and add the milk. Use a balloon whisk to whisk until well combined. Return the pan to the heat. Cook, stirring, for 2 mins or until sauce boils and thickens. Remove from heat. Add half the gruyère or Swiss cheese and half the cheddar. Stir until the cheese melts and mixture is combined. Season to taste.

Heat a barbecue grill or chargrill on medium. Brush the bread evenly with remaining butter. Cook the bread on the grill for 1 min or until lightly toasted underneath. Transfer, toasted-side up, to a clean work surface. Spread half the bread with mustard. Spread with cheese sauce. Top with ham. Sprinkle with remaining gruyère or Swiss cheese and remaining cheddar. Top with remaining butter, toasted-side down.

Cook the sandwiches on the grill for 2-3 mins each side or until the bread is golden brown and the filling is heated through. Cut in half and serve immediately.