1. Lightly warm and crisp up baguette slices on a hot grill, about 30-45 seconds, until lightly marked.
2. Mix together butter, parsley, black pepper, and truffle oil.
3. Finely grate half of the truffle into the butter and mix.
4. Spread butter over warm bread.
5. Add sliced prosciutto and Serrano ham over the butter.
6. Grate horseradish and remaining truffle over the top.