Please find below the code that is generated for those two buttons (cart and heart). I havent found yet which file is used to generate this
<div class="hikashop_product_stock">
<a rel="nofollow" class="hikashop_cart_button" href="#" onclick="var field=document.getElementById('hikashop_product_quantity_field_2');return hikashopModifyQuantity('2355',field,1,0,'cart',154)">ajouter au panier</a>
<input id="hikashop_product_quantity_field_2" type="hidden" value="1" class="hikashop_product_quantity_field" name="quantity">
<div id="hikashop_add_wishlist">
<a rel="nofollow" class="hikashop_cart_button" href="#" onclick="var field=document.getElementById('hikashop_product_quantity_field_2');if(hikashopCheckChangeForm('item',hikashop_product_form)){ var typeField = document.querySelector('form[name=hikashop_product_form] input[name=cart_type]'); if(typeField !== null){typeField.value = 'wishlist';} return hikashopModifyQuantity('2355',field,1,hikashop_product_form,'wishlist',154); } else { return false; }">ajouter à vos souhaits</a>
</div>
</div>