Butter 24 small muffin cups. Cut bread slices into rounds with a 3-inch (7.5 cm) cookie cutter. Press bread rounds into muffin cups and put in a 400°F (200°C) oven for 10 minutes, or until edges are lightly browned. Cool.

The cups can be placed on cookie sheets and frozen, then stored in plastic bags or rigid containers in the freezer for later use.

To make filling, wipe mushrooms with damp paper towel; chop fine. In a large skillet, melt butter; add mushrooms and green onion, and sauté until all moisture from mushrooms has evaporated. Do not brown. Sprinkle flour over mushrooms and cook, stirring, for a minute or so. Remove from heat. Add milk and salt, and mix well. Return to heat and cook, stirring constantly, until mixture thickens. Season to taste with cayenne, parsley and lemon juice.

If frozen, replace bread cups in the muffin tins and thaw slightly. Or continue with the freshly baked cups, which have been cooled in the tins. Use a piping bag (or spoon) to fill each bread cup with filling and sprinkle a little parmesan cheese on top. Bake at 350°F (180°C) for 10 minutes, or until filling is hot and cheese is golden brown. Makes 24 appetizers.

Note: The mushroom filling may be frozen before assembling, or refrigerated for up to 4 days in advance.

Tip: Use leftover bread ends to make dry bread crumbs for future use. Place bread on cookie sheets and put in a 350°F (180°C) oven for 30 to 45 minutes, until dry and slightly toasted. Process into crumbs in a food processor or blender (or place in a plastic bag and roll into crumbs with a rolling pin).