There are many options here. You can either buy prepared gulab jamuns from the store, make them from a mix or from scratch.
I used MTR gulab jamun mix to make mine.
Grind almonds and cashews to a fine powder. Add this to the gulab jamun mix along with 1tsp ground cardamom. Add milk a little at a time and mix and knead to form a smooth dough. Cover and set aside for 5 minutes.
Combine sugar and water in a saucepan; bring the mixture to a boil and simmer for 5~6 minutes. Add the remaining 1tsp of ground cardamom and turn off the heat and set it aside.
Heat oil or ghee for deep frying the jamuns. Divide the gulab jamun dough into 18~20 little pieces. Roll them into smooth balls making sure that there are no cracks.
Gently slide them into the hot oil and fry on medium-low flame until they are nicely cooked through and golden brown outside. Remove with a slotted spoon and put them into the sugar syrup.
Let the gulab jamuns soak in the syrup for 30 minutes. Remove them from the syrup place them on a plate. Reserve the sugar syrup and refrigerate the gulab jamuns for at least 1 hour.
Cut the gulab jamuns in half and keep ready.