What is the best way to introduce shellfish/peanuts, or other possible allergy "risky" foods to a one year old?

Now : Recent studies suggest that introducing table foods to infant between age 4 and 6 months reduce the development of food allergy. This is opposite of what we had recommended just a couple of years earlier. For a child with eczema or a family history of peanut allergy, you should consult your allergist before going ahead since the issue is more complicated.

Allergy to fish nuts: Controversial subject! but current guidelines, do not limit the introduction of "highly allergenic foods" to children; parents can introduce nuts and shellfish as other foods are introduced, after 6 months of age. If a child has a strong personal or family history of allergic symptoms (atopic dermatitis, allergic rhinitis or asthma), have a consultation with a local allergist/immunologist.

One at a time: It is safe to do so now at this age, just do them one at a time separated by a couple of days. If there is any reaction, you can pinpoint the source easier.