Mix the spicy sauce ingredients together in a small bowl and set aside.
Heat the oil in a large frying pan over a medium-high heat. Add the beef, and use the back of a spoon to break it up. Cook the beef until it is browned all the way through. Add the garlic and cook for an additional minute.
Add the spicy sauce mixture to the pan and stir to thoroughly mix through. Cook the beef mixture for approximately 5 minutes, until the liquid has evaporated. Continue cooking the beef for another 2 minutes, allowing the sugars to caramelise.
Add the water and cook the beef for 1 minute.
Meanwhile, heat a second frypan over medium heat. Add the butter and let it melt. Add the spinach and sauté for 1-2 minutes. Remove from the heat and season.
To serve, divide the rice among 4 bowls. Top each bowl with beef mixture, sauted spinach, julienned carrots and some slices of cucumber. Drizzle with extra sriracha sauce and sprinkle sesame seeds over the top of everything.