diff --git a/packages/cactus-core/package.json b/packages/cactus-core/package.json
index 3e2dea8a26..3900846b19 100644
--- a/packages/cactus-core/package.json
+++ b/packages/cactus-core/package.json
@@ -52,6 +52,7 @@
   "dependencies": {
     "@hyperledger/cactus-common": "2.0.0-alpha.2",
     "@hyperledger/cactus-core-api": "2.0.0-alpha.2",
+    "body-parser": "1.20.2",
     "express": "4.19.2",
     "express-jwt-authz": "2.4.1",
     "express-openapi-validator": "5.0.4",
@@ -62,6 +63,7 @@
     "typescript-optional": "2.0.1"
   },
   "devDependencies": {
+    "@types/body-parser": "1.19.4",
     "@types/express": "4.17.19",
     "@types/http-errors": "2.0.2",
     "node-mocks-http": "1.14.0",
diff --git a/packages/cactus-core/src/main/typescript/public-api.ts b/packages/cactus-core/src/main/typescript/public-api.ts
index 6e748c5696..c0a833fb24 100755
--- a/packages/cactus-core/src/main/typescript/public-api.ts
+++ b/packages/cactus-core/src/main/typescript/public-api.ts
@@ -23,3 +23,9 @@ export {
   IHandleRestEndpointExceptionOptions,
   handleRestEndpointException,
 } from "./web-services/handle-rest-endpoint-exception";
+
+export { stringifyBigIntReplacer } from "./web-services/stringify-big-int-replacer";
+
+export { IConfigureExpressAppContext } from "./web-services/configure-express-app-base";
+export { configureExpressAppBase } from "./web-services/configure-express-app-base";
+export { CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER } from "./web-services/configure-express-app-base";
diff --git a/packages/cactus-core/src/main/typescript/web-services/configure-express-app-base.ts b/packages/cactus-core/src/main/typescript/web-services/configure-express-app-base.ts
new file mode 100644
index 0000000000..79b3a047a3
--- /dev/null
+++ b/packages/cactus-core/src/main/typescript/web-services/configure-express-app-base.ts
@@ -0,0 +1,91 @@
+import type { Express } from "express";
+import bodyParser, { OptionsJson } from "body-parser";
+
+import {
+  Checks,
+  LogLevelDesc,
+  LoggerProvider,
+} from "@hyperledger/cactus-common";
+
+import { stringifyBigIntReplacer } from "./stringify-big-int-replacer";
+
+export const CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER =
+  "CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER";
+
+/**
+ * Implementations of this interface are objects who represent a valid execution
+ * context for the `configureExpressAppBase()` utility function.
+ *
+ * @see {configureExpressAppBase}
+ * @see {ApiServer}
+ */
+export interface IConfigureExpressAppContext {
+  readonly logLevel?: LogLevelDesc;
+  readonly app: Express;
+  readonly bodyParserJsonOpts?: OptionsJson;
+}
+
+/**
+ * Configures the base functionalities for an Express.js application.
+ *
+ * The main purpose of this function is to have a reusable implementation
+ * of the base setup logic that the API server does. For test cases of
+ * plugins we can't directly import the API server because it would cause
+ * circular dependencies in the mono-repo that usually ends up causing mayhem
+ * with the build in general and also with the architecture longer term.
+ *
+ * So, with this function being here in the core package it makes it easy
+ * to reuse by both plugin test cases and also the API server itself.
+ *
+ * The logic here is kept very small because the order of the ExpressJS
+ * middleware handler's matters a lot and if you mix up the order then
+ * new bugs can appear.
+ *
+ * @param ctx The context object holding information about the log level
+ * that the caller wants and the ExpressJS instance itself which is to be
+ * configured.
+ *
+ * @throws {Error} If any of the required context properties are missing.
+ */
+export async function configureExpressAppBase(
+  ctx: IConfigureExpressAppContext,
+): Promise<void> {
+  const fn = "configureExpressAppBase()";
+  Checks.truthy(ctx, `${fn} arg1 ctx`);
+  Checks.truthy(ctx.app, `${fn} arg1 ctx.app`);
+  Checks.truthy(ctx.app.use, `${fn} arg1 ctx.app.use`);
+
+  const logLevel: LogLevelDesc = ctx.logLevel || "WARN";
+
+  const log = LoggerProvider.getOrCreate({
+    level: logLevel,
+    label: fn,
+  });
+
+  log.debug("ENTRY");
+
+  const didRun = ctx.app.get(CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER);
+  if (didRun) {
+    const duplicateConfigurationAttemptErrorMsg =
+      `Already configured this express instance before. Check the ` +
+      `configuration variable of the ExpressJS instance under the key ` +
+      `"CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER" to determine if an ` +
+      `instance has already been `;
+    throw new Error(duplicateConfigurationAttemptErrorMsg);
+  }
+
+  const bodyParserJsonOpts: OptionsJson = ctx.bodyParserJsonOpts || {
+    limit: "50mb",
+  };
+  log.debug("body-parser middleware opts: %o", bodyParserJsonOpts);
+
+  const bodyParserMiddleware = bodyParser.json(bodyParserJsonOpts);
+  ctx.app.use(bodyParserMiddleware);
+
+  // Add custom replacer to handle bigint responses correctly
+  ctx.app.set("json replacer", stringifyBigIntReplacer);
+
+  ctx.app.set(CACTI_CORE_CONFIGURE_EXPRESS_APP_BASE_MARKER, true);
+
+  log.debug("EXIT");
+}
diff --git a/packages/cactus-core/src/main/typescript/web-services/stringify-big-int-replacer.ts b/packages/cactus-core/src/main/typescript/web-services/stringify-big-int-replacer.ts
new file mode 100644
index 0000000000..ff77ddbffc
--- /dev/null
+++ b/packages/cactus-core/src/main/typescript/web-services/stringify-big-int-replacer.ts
@@ -0,0 +1,13 @@
+/**
+ * `JSON.stringify` replacer function to handle BigInt.
+ * See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt#use_within_json
+ */
+export function stringifyBigIntReplacer(
+  _key: string,
+  value: bigint | unknown,
+): string | unknown {
+  if (typeof value === "bigint") {
+    return value.toString();
+  }
+  return value;
+}
diff --git a/packages/cactus-core/src/test/typescript/unit/web-services/configure-express-app-base.test.ts b/packages/cactus-core/src/test/typescript/unit/web-services/configure-express-app-base.test.ts
new file mode 100644
index 0000000000..05cdaea4d7
--- /dev/null
+++ b/packages/cactus-core/src/test/typescript/unit/web-services/configure-express-app-base.test.ts
@@ -0,0 +1,18 @@
+import "jest-extended";
+import express from "express";
+
+import { configureExpressAppBase } from "../../../../main/typescript/public-api";
+
+describe("configureExpressAppBase()", () => {
+  test("Crashes if missing Express instance from ctx", async () => {
+    const invocationPromise = configureExpressAppBase({} as never);
+    await expect(invocationPromise).toReject();
+  });
+
+  test("Does not crash if parameters were valid", async () => {
+    const app = express();
+    await expect(
+      async () => await configureExpressAppBase({ app, logLevel: "DEBUG" }),
+    ).not.toThrow();
+  });
+});
diff --git a/yarn.lock b/yarn.lock
index 09e8f0b711..cc281b5e54 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7916,8 +7916,10 @@ __metadata:
   dependencies:
     "@hyperledger/cactus-common": "npm:2.0.0-alpha.2"
     "@hyperledger/cactus-core-api": "npm:2.0.0-alpha.2"
+    "@types/body-parser": "npm:1.19.4"
     "@types/express": "npm:4.17.19"
     "@types/http-errors": "npm:2.0.2"
+    body-parser: "npm:1.20.2"
     express: "npm:4.19.2"
     express-jwt-authz: "npm:2.4.1"
     express-openapi-validator: "npm:5.0.4"