Place beans in a sieve and rinse well with cold water. Drain.
Peel and thinly slice garlic. Rinse rosemary and shake dry.
In a pan, heat oil and rosemary over low heat. Add garlic and cook until golden brown.
Add beans and 50 ml water (approximately 1/4 cup). Simmer over low heat for 5 minutes. Remove rosemary.
Transfer beans to a bowl. Mash with a potato masher. Juice lemon. Season beans with salt, pepper and lemon juice (to taste).