I think the adult population of the western world hate you for asking this question. lol
Anyway, I'm still about 8kgs off my BMI and dropping slowly so I don't share your plight yet.
My best advice is target the things that are highest in kilojoules but the things we desperately need for maximum effect like the good omega 3 oils in fish and flaxseed, complex carbohydrates in brown rice, lentils and baked potato. Olive oil is neutral but high in kilojoules. Just watch that your saturated fat doesn't breach the 20gram mark. Remember that the Prof. says Swank didn't count bread so go for it.
In your adventageous situation for dinner for example I would grill a beautiful piece of fresh fish with veges, brown rice with tomatoes, shallots,capsicum, pine nuts, raisens, olive oil and soy sauce, and throw in a baked potato topped with the cauliflower butter recipe from another post. Then finish with a ripe mango and other fresh fruits. For later on I couldn't go past a freshly toasted thick slice of ciabatta bread topped with peanut butter (2.5grams of sat. fat) banana and generous serving of honey. The problem will be your stomach won't fit all that in for one meal so you'll need to pace yourself and eat every few hours.
Sorry if this sounds overly simple but you know the real secret to dieting success is to know your daily kilojoule intake minus you daily kilojoule output including your resting metabolic rate. Success will be guaranteed.
For example for women this calculation to determine your resting metabolic rate is:
[655.1 + (9.56 x weight in kilograms) + (1.85 x height in centimetres) - (4.68 x age)] x 4.2
Once you work out your resting metabolic rate then you'll need to multiply this number by an activity factor depending on how much exercise you do per week:
Sedendary x 1.2
Lightly active x 1.375
Moderate x 1.55
Very active x 1.725
Extreme x 1.9
You need to eat 2000 - 4000 kilojoules more day to gain 0.5 - 1.0kg per week.
So get eating and enjoy this delicious vegan plus seafood diet. I look forward to calling you both 'fatso' soon.