The Nim language's compiler is written in Nim, but they provide transpiled C code to bootstrap from. Except this isn't really bootstrapping, because the generated C is hardly readable. Turns out that the oldest versions of Nim were written in Object Pascal, using the Free Pascal Compiler, but that isn't bootstrappable either! So, bootstrapping Pascal is a prerequisite to bootstrapping Nim; see the Aesop page for details.
Once Aesop is complete, I'll update this page with more information about the chain from Pascal-Nim to the latest Nim.