I have an induction cooktop in my island powered by a 40 amp circuit, can I spur off this to install two outlets on the side of the island?
No, you cannot tap off of a 40 amp circuit for receptacle circuits.
According to the National Electrical Code Article 210.21(B) and Table 210.21(B)(3) Receptacles connected to a 40 amp circuit would have to be rated 40 or 50 amps. Kinda tough to plug your toaster in to those.

210.21(B)(3) Receptacle Ratings.  Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

Here are two other places in the National Electrical Code that cover kitchen branch circuits.
The exception below allows you to power cooking equipment from a 50 amp branch circuit but not receptacles from a 40.

210.19 (A) (3) Household Ranges and Cooking Appliances.  Branch-circuit conductors supplying household ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances shall have an ampacity not less than the rating of the branch circuit and not less than the maximum load to be served. For ranges of 83∕4 kW or more rating, the minimum branch-circuit rating shall be 40 amperes.
Exception No. 1: Conductors tapped from a 50-ampere branch circuit supplying electric ranges, wall-mounted electric ovens, and counter-mounted electric cooking units shall have an ampacity of not less than 20 amperes and shall be sufficient for the load to be served. These tap conductors include any conductors that are a part of the leads supplied with the appliance that are smaller than the branch-circuit conductors. The taps shall not be longer than necessary for servicing the appliance.

The Code requires a minimum of 2 20 amp Small-Appliance to serve the counter tops in the kitchen. The pertinent article is below:

210.11(C) Dwelling Units.
(1) Small-Appliance Branch Circuits.  In addition to the number of branch circuits required by other parts of this section, two or more 20-ampere small-appliance branch circuits shall be provided for all receptacle outlets specified by 210.52(B).

Kitchen island counters require enough receptacles so no part of the counter is more than 24 inches from a receptacle.

210.52(C) Countertops and Work Surfaces. In kitchens, pantries, breakfast rooms, dining rooms, and similar areas of dwelling units, receptacle outlets for countertop and work surfaces shall be installed in accordance with 210.52(C)(1) through (C)(5).
(1) Wall Countertop and Work Surface. A receptacle outlet shall be installed at each wall countertop and work surface that is 300 mm (12 in.) or wider. Receptacle outlets shall be instal‐ led so that no point along the wall line is more than 600 mm (24 in.) measured horizontally from a receptacle outlet in that space.
Exception: Receptacle outlets shall not be required on a wall directly behind a range, counter-mounted cooking unit, or sink in the installa‐ tion described in Figure 210.52(C)(1).
(2) Island Countertop Spaces.  At least one receptacle shall be installed at each island countertop space with a long dimension of 600 mm (24 in.) or greater and a short dimension of 300 mm (12 in.) or greater.

So, you need some receptacles on the island. And you can't feed them from taps off of the 40 amp circuit. However, you could put a sub-panel on the island as Tyson points out. The problem with this idea is the cooktop takes the entire capacity of your sub-panel.
The best thing to do would be to run #12 AWG wire for one or more circuits to the island.
Good luck!