1. Mix the mustard with a little ale to make a paste in the base of a pan. Stir in the rest of the ale, the butter and Worcestershire sauce over a gentle heat and cook for about 5 minutes, until the butter has melted.
2. Add the cheese and cook for a further 5 minutes, stirring occasionally and being careful that the mixture doesn’t boil, until melted and smooth. Season, then remove from the heat and allow to cool slightly. Beat the yolks into the just-warm but still melted cheese.
3. Preheat the grill to high and toast the bread lightly on both sides, then leave to cool on the grill rack.
4. Spread the cheese mixture over the cooled toast and grill for 3-4 minutes or until bubbling and golden. Coarsely grate the pear and immediately toss with the lemon juice.
Stir in the walnuts and parsley. Cut each toast into 4 slices and serve with the relish, ready to spoon on top.