A placer dans fichier template
<a href="<?php echo wc_get_cart_url() ?>" class="misha-cart"><?php echo $woocommerce->cart->cart_contents_count ?></a>
A placer dans functions
add_filter( 'woocommerce_add_to_cart_fragments', 'misha_add_to_cart_fragment' );
function misha_add_to_cart_fragment( $fragments ) {
global $woocommerce;
$fragments['.misha-cart'] = '<a href="' . wc_get_cart_url() . '" class="misha-cart">'. $woocommerce->cart->cart_contents_count . '</a>';
return $fragments;
}