For two servings:
2 Tbl olive oil
1 Tbl chopped garlic
1/4 cup chopped yellow onion
1/3 pound breakfast sausage
2 Tbl butter
2 Tbl flour
1 cup whole milk (approximately)
black pepper
Heat the oil over medium heat, then add onions and garlic and sweat for 2-3 minutes, until onion is translucent. Add the sausage, and cook through.
Add the butter and stir until it melts. Add the flour, and stir in to make a paste. When the flour has disappeared, add a splash of milk and mix it in with a spatula. Continue to add splashes of milk until you get the consistency you want. It should end up more or less like pancake batter. Season to taste with black pepper.
Note that it will thicken as it sits on the stove, so keep the milk handy to re-thin as necessary.