My dd had chocolate from around 6 months!! - I dont see a real need to wait until 3 years unless you have a history of dairy intolerance. Re: peanut butter, that also depends on a family history of allergic disease/food allergy.
According to the Babycentre website:
women who have a family history of allergic disease (or who have a partner who does) may wish to avoid peanuts and peanut products while pregnant and breastfeeding to reduce the risk of their baby developing a peanut allergy. Allergic diseases include asthma, eczema, hay fever and food allergies. It also recommends that babies from families with a history of allergic disease stay on a peanut-free diet until the age of three years.
If you have a family history of allergic disease, you may also choose to exclude all nuts from your baby's diet, not just peanuts. The reason for this is that, if a child is allergic to peanuts, they may be allergic to some other nuts. This is because the proteins found in peanuts and other nuts have a very similar structure.
If you have no family history of allergic disease, these recommendations do not apply and peanuts can be included in both your own and your baby's diet. In fact, peanut butter can be a useful weaning food. It is highly nutritious, and a good source of protein, particularly for vegetarian and vegan babies.
If you are using nuts in your baby's or toddler's diet, do make sure they are ground or processed into small pieces, so that your baby can't choke on them. (Children under five should not be given any whole nuts because of the risk of choking.)
If you do not have a history of allergy in the family, you can give your baby ground nuts and nut spreads, including peanut butter, from six months.
My dd loves peanut butter(smooth) and jam sandwiches
Seona
