CPP MSVS Including header files across projects causing unresolved externals

Question

I have 2 projects, containing 3 files

---

ProjectOne

Entry.cpp // Entry point, main()

#include "../ProjectTwo/ExternalClass.h"

int main()
{
    ExternalClass::Function();
    return 1;
}

---

ProjectTwo

ExternalClass.h // ExternalClass::Function() Declaration

#pragma once
class ExternalClass
{
public:
    static void Function();
};

ExternalClass.cpp // ExternalClass::Function() Definition

#include "ExternalClass.h"

void ExternalClass::Function()
{
    return;
}

---

Project one includes project two's ExternalClass.h file. In the entry point of project one, I call ExternalClass::Function(), In result I get

Severity Code Description Project File Line Suppression State Error LNK2019 unresolved external symbol "public: static void __cdecl ExternalClass::Function(void)" (?Function@ExternalClass@@SAXXZ) referenced in function _main ProjectOne ...\ProjectOne\Entry.obj 1

In attempt to fix this I tried making project one dependant on project two, I set project two to a project with no entry point, and it builds as a utility file,

How do I fix this?