What type of sentence is an éclair-a long, thin, frosted pastry-is traditionally filled with vanilla cream, but its flavor can be enhanced with other fillings, such as chocolate, coffee, strawberry, or pistachio?

This is a compound sentence.

A compound sentence contains at least two independent clauses. An independent clause is a clause that can exist on its own, unlike dependent clauses. In the sentence above, there are two independent clauses:

1. A n éclair-a long, thin, frosted pastry-is traditionally filled with vanilla cream

2. (But) I ts flavor can be enhanced with other fillings, such as chocolate, coffee, strawberry, or pistachio