1Heat oven to 350 F. In a medium skillet melt 1 tablespoon butter and olive oil over medium heat. Add breadcrumbs, garlic, and thyme, stirring occasionally until golden and toasted, about 3 minutes. Season to taste with salt and pepper. Set aside.
2In a large saucepan, melt remaining 3 tablespoons butter over medium heat. Add onions and sauté until translucent and soft, about 5 minutes. Whisk in flour until completely incorporated with butter and onions, cooking until the mixture starts to bubble a little, about 2 minutes more. Continue to whisk and slowly pour in beer, then cream, whisking until blended, making sure flour mixture does not stick to bottom of pan. Let mixture come to a boil, whisking constantly. Once mixture comes to a boil, reduce heat and let simmer, whisking occasionally, 3 minutes. Increase heat to medium and add cheeses, stirring until completely melted and smooth. Season to taste with salt and pepper.
3Transfer cooked macaroni to a large mixing bowl. Pour cheese sauce over macaroni, then add lobster meat and stir well to combine. Transfer to a 1 ½ quart baking dish. Sprinkle seasoned breadcrumbs over top and bake until sauce is bubbly, about 25 to 30 minutes.