Season steaks with salt and pepper and set aside in refrigerator.
Heat butter in a medium saucepan over medium heat until bubbling. Crush garlic. Add garlic, onion and carrot to saucepan. Cook, stirring, until onion is translucent, about 4 minutes. Add stock and maple syrup, then increase heat to high and boil 10 minutes, or until liquid is reduced to about 1/2 cup. Add beer, bring to a simmer, then remove from heat.
Grill or broil steaks. Let rest 5 minutes.
Add rosemary to sauce. Return sauce to medium-high heat and bring to a simmer. Season with salt and pepper. Strain sauce.
Slice steak thinly across the grain. Spoon sauce over meat and serve.