Pour the Guinness into a small saucepan over medium-high heat. Bring to a simmer and reduce until the liquid measure approximately ⅓ cup.
Thread the beef onto skewers and season with steak seasoning. Heat a flat stop griddle, grill pan or large skillet over high heat. Drizzle the skewers with olive oil.
Add the skewers to the pan and brush the top generously with the Guinness reduction using a basting brush. Sear the steak for 2-3 minutes before rotating the skewers ¼ turn, again brushing the reduction on the top side. Repeat until all four sides have been seared and all the reduction has been used. Turn the skewers to coat them in the boiled down Guinness sauce on the pan. Remove to a serving platter.
Meanwhile, in a small saucepan over medium heat, melt the butter. Whisk in the flour and cook for 1-2 minutes, then slowly whisk in the milk. Once the milk has thickened to a cream-like thickness, whisk in the gouda, ⅓ a time, waiting to add the next batch until the previous one is fully incorporated. Season with freshly ground pepper and pour into a small bowl. Serve alongside the skewers.
You can use your preferred cut of steak. Tenderloin, of course, is wonderful, but even sirloin does the job well!